Report to the Air Resources Board on the Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant Part A Exposure Assessment As Approved by the Scientific Review Panel on April 22, 1998 Project Manager Robert K. Krieger Reviewed by Janette M. Brooks, Manager Substance Evaluation Section Genevieve A. Shiroma, Chief Air Quality Measures Branch Donald J. Ames, Assistant Chief Stationary Source Division Peter D. Venturini, Chief Stationary Source Division ACKNOWLEDGMENTS
Transcript
Report to the Air Resources Boardon the Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant
Part A
Exposure Assessment
As Approved by the Scientific Review Panelon April 22, 1998
Project Manager
Robert K. Krieger
Reviewed by
Janette M. Brooks, ManagerSubstance Evaluation Section
Genevieve A. Shiroma, ChiefAir Quality Measures Branch
Donald J. Ames, Assistant ChiefStationary Source Division
Peter D. Venturini, ChiefStationary Source Division
ACKNOWLEDGMENTS
The following people helped prepare this draft report by providing information, writing sectionsof the report, comments, or review: Janey Arey and Roger Atkinson (Statewide Air PollutionResearch Center, University of California, Riverside); Barbara Zeilinska (Desert ResearchInstitute); Joan Denton (Office of Environmental Health Hazard Assessment); and Don Chernich, Steve Church, Joe De Vita, Andy Delao, Michele Houghton, Kelly Hughes, Steve Hui, Paul Jacobs, Peggy Jenkins, Jackie Johnson, Martin Johnson, Bill Lovelace, Susan Lum, Chris Nguyen, Elizabeth Parkhurst, Ralph Propper, Andy Ranzieri, Tony Servin, andJeff Wright (ARB).
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REPORT TO THE AIR RESOURCES BOARD ON DIESEL EXHAUST
Part A - Public Exposure To, Sources and Emissions of Diesel Exhaust in California
This document, prepared by staff of the Air Resources Board (ARB), contains the staff'sevaluation of atmospheric exposure to diesel exhaust in California. It is Part A of the TechnicalSupport Document Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant, andwas developed under the authority of California's Toxic Air Contaminant (TAC) Program(Assembly Bill 1807: Health and Safety Code sections 39660-39662).
This report contains the staff evaluation of diesel exhaust PM and PM (particulate10 2.5
matter equal to or less than 10 and 2.5 microns in diameter, respectively) emissions, outdoorambient and indoor air concentrations, potential near source exposures, statewide population-weighted exposures including an estimate of total exposure, and atmospheric persistence and fate.
Diesel exhaust is a complex mixture of inorganic and organic compounds that exist ingaseous, liquid, and solid phases. As with other fuel combustion sources, the primary gaseouscomponents are nitrogen (N ), oxygen (O ), carbon dioxide (CO ), and water vapor (H O). 2 2 2 2
Some of the exhaust components, like arsenic, benzene, and nickel, are known to cause cancer inhumans. Over 40 components of the exhaust, including suspected human carcinogensbenzo[a]pyrene, 1,3-butadiene, and formaldehyde, have been listed as TACs by the ARB, and ashazardous air pollutants by the U.S. EPA.
One of the main characteristics of diesel exhaust is the release of particles at a rate of about20 times greater than from gasoline-fueled vehicles (WHO, 1996). Diesel exhaust particles carrymany of the harmful organics and metals present in the exhaust. The particles are typically smallerthan 1 micrometer [(Fm) 1 millionth of a meter] in diameter, and are easily inhaled into thebronchial and alveolar regions of the lung.
The combustion of diesel fuel in an internal combustion engine produces diesel exhaust. Approximately 2.1 billion gallons of diesel fuel were burned in internal combustion engines inCalifornia during 1995. The future estimated diesel fuel consumption is predicted to increase inCalifornia from current levels up to 2.3 billion gallons in 2000 to 2.9 billion gallons in 2010.
Three major sources emit diesel exhaust in California: mobile sources (on-road vehicles andother mobile sources), stationary area sources (i.e. oil and gas production facilities, shipyards,repair yards), and stationary point sources (i.e., chemical manufacturing, electric utilities). Emissions of carbon monoxide (CO), oxides of nitrogen (NO ), oxides of sulfur (SO ), reactivex x
organic gases (ROG), PM , and PM are estimated in this report. For 1995, emissions of diesel10 2.5
exhaust CO are estimated to be about 188,000 tons per year (tpy); NO to be about 415,000 tpy;X
SO to be about 28,000 tpy; and ROG to be about 41,000 tpy. Diesel exhaust PM and PMx 10 2.5
emissions during 1995 were estimated to be about 27,000 tpy and 26,000 tpy, respectively.
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Statewide emission estimates for other substances found in diesel exhaust are not known (i.e. listof TACs in Table III-1). Further research is needed to estimate emissions from these substances.
In this report, California's population exposure to fine diesel exhaust particulate matter(PM ) is discussed in more detail because more is known about the particulate fraction, and many10
researchers believe that the diesel exhaust particles contain many of the toxic components of theexhaust. However, the exposure actually experienced in most health studies, particularly thehuman studies, has been to the overall exhaust. Until more research is done to identify thespecific causes of toxicity in diesel exhaust, the identification of whole diesel exhaust is consistentwith the basis of health studies.
To estimate Californian’s outdoor ambient exposures to diesel exhaust PM , ARB staff used10
receptor modeling techniques, which includes chemical mass balance model results from severalstudies, ambient 1990 PM monitoring network data, and 1990 PM emissions inventory data. 10 10
The staff used the 1990 PM inventory and monitoring data as the basis for calculating the10
statewide exposure to diesel exhaust PM because it would best represent the emission sources in10
the years when the ambient data were collected for the studies used to estimate 1990 dieselexhaust PM outdoor concentrations. The staff estimated a population-weighted average10
outdoor diesel exhaust PM exposure concentration in California in 1990 to be 3.0 micrograms10
per cubic meter (Fg/m ). The staff have also estimated outdoor exposure concentrations for 19953
based on linear extrapolations from the base year 1990 to the 1995 emissions inventories. The estimated 1995 outdoor ambient concentration in California is 2.2 Fg/m .3
Near-source exposures to diesel exhaust may occur near busy roads and intersections wherediesel vehicles are operating. In December 1993, the ARB conducted a study to determine dieselexhaust PM concentrations due to emissions of diesel exhaust particles near a freeway. Results10
indicate that diesel exhaust PM concentrations may be up to five times above 1995 average10
outdoor ambient concentrations of 2.2 Fg/m and about six times above the 1995 total air3
exposure concentration of 1.5 Fg/m .3
To estimate Californian’s indoor and total air exposure to diesel exhaust particles, the staffused the 1990 population-weighted outdoor ambient concentration estimates in a model that canestimate indoor air concentrations and total air exposure. The exposure modeling results indicatethat, in 1990, Californian’s were exposed to average diesel exhaust particle concentrations of 2.0 Fg/m and 2.1 Fg/m for indoor and total air exposure scenarios, respectively. The staff have3 3
also estimated indoor and total air exposure concentrations for 1995. These estimates were notdeveloped using the model used in calculating the 1990 indoor and total air exposure estimates. Instead, the staff used the ratios of indoor and total air exposure concentrations to outdoorambient exposure concentrations and applied these to the 1995 outdoor ambient concentrationestimate to calculate 1995 indoor and total air exposure concentrations. The estimated 1995 indoor and total air exposure concentrations are 1.47 Fg/m (rounded to 1.5 Fg/m ) and 3 3
1.54 Fg/m (rounded to 1.5 Fg/m ), respectively. 3 3
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As mentioned above, diesel exhaust is a complex mixture of substances, and each substancewill remain in the air or react with other substances according to the substance’s individualchemical properties. The diesel particles are typically smaller than 1 micron and are expected toremain in the air for about 10 days.
Over the past 20 years, several advances in engine design and fuel formulation have beenmade in reducing diesel exhaust emissions as a result of control measures that have been adoptedby the ARB and U.S. EPA. For example, as part of California’s overall program to reduceharmful exposures to particulate matter, current and in the future, the ARB and the U.S. EPAhave adopted a series of mobile source standards and regulations to reduce diesel exhaust PM10
emissions (see Chapter IV). As a measure of the effectiveness of these standards and regulations,statewide diesel exhaust PM emissions from on-road mobile sources are expected to be reduced10
by approximately 80 percent between 1990 and 2010 or about 60 percent from 1995 to 2010.
The U.S. EPA has also adopted a National Ambient Air Quality Standard (NAAQS) forPM (particulate matter equal to or less than 2.5 microns in diameter). The federal Clean Air Act2.5
requires that the U.S. EPA establish NAAQS’ and reassess, at least every five years, whetheradopted standards are adequate to protect public health based on current scientific evidence. After review, the U.S. EPA’s Clean Air Scientific Advisory Committee (CASAC) found thatcurrent PM standards do not adequately protect public health. For this reason, on10
July 18, 1997, the U.S. EPA adopted an annual PM federal standard of 15 micrograms per2.5
cubic meter (Fg/m ) and a 24-hour federal standard of 65 Fg/m . The addition of the PM3 32.5
standards will result in substantially more health protection than the current federal PM10
standards alone. We are looking at how this standard may affect the need for further diesel engineexhaust particle controls, realizing that a larger percentage of the fine PM inventory (as2.5
compared to PM inventory) is due to petroleum-based fuel combustion sources. 10
Diesel exhaust is in the identification (risk assessment) phase of our air toxics program. While no new control measures specific to the toxicity of diesel exhaust are being proposed at thistime, a number of existing sources of diesel engine exhaust are already subject to Californiaregulations requiring reductions of criteria air pollutants contained in diesel exhaust. If dieselexhaust is identified as a TAC, the ARB will begin a full, open public process to evaluate theneed, feasibility, and cost of control to determine if any regulatory action is necessary to reducethe risk of exposure to diesel exhaust.
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II.INTRODUCTION
This report (Part A) consists of the ARB staff evaluation of the public exposures to, sourcesand emissions of diesel exhaust in California. It provides the exposure assessment portion of theevaluation of diesel exhaust as a toxic air contaminant (TAC), pursuant to California’s Toxic AirContaminant Program (Health and Safety Code section 39660). The Office of EnvironmentalHealth Hazard Assessment (OEHHA) has developed a comprehensive health evaluation of dieselexhaust (Part B report). Together, these documents serve as the basis for ARB’s proposedidentification of diesel exhaust as a TAC.
Diesel exhaust entered into the identification program in October 1989. In March 1990,the ARB sponsored a conference on the risk assessment of diesel exhaust. On June 17, 1994, the first draft report was released to the public for a six month comment period. On September 14, 1994, a public workshop was held to discuss the report. On January 29-30, 1996,the OEHHA, ARB, Health Effects Institute, National Institute for Occupational Safety andHealth, World Health Organization, and the U.S. EPA sponsored a scientific workshop to discussthe application of human health study data in developing quantitative cancer risk estimates fordiesel exhaust. A second version of the draft report was released for public comment inMay 1997. On July 1, 1997, a third public workshop was held to discuss the second draft of thereport.
This version of the report reflects the public comments received on the exposure assessmentduring the first and second public comment periods and at the September 1994, January 1996,and July 1997 workshops. Currently, the SRP is planning to hold a special public meeting in earlyMarch 1998 to hear from invited scientists, with expertise in the study of diesel exhaust, to heartheir research and perspectives on diesel exhaust health effects. It is the SRP’s view that thematerial presented and discussed at this meeting will assist in a better understanding of the scienceregarding the health effects of diesel exhaust. After this meeting, and the end of the thirdcomment period, the report, along with the comments received and any revisions resulting fromthe comments, will be formally discussed with the SRP at a duly noticed meeting. We anticipatethat this meeting will occur in late April 1998. If the SRP approves the report, the report, and aproposal to formally list diesel exhaust as a TAC, will be presented to the ARB at a publichearing, after a 45-day comment period.
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III.CHEMICAL AND PHYSICAL PROPERTIES OF DIESEL EXHAUST
Diesel exhaust is a complex mixture that contains thousands of inorganic and organicsubstances (IARC, 1989) which occur in the form of gases and fine particles (composed of liquidand solid materials). The composition of this mixture will vary depending on engine type,operating conditions, fuel, lubricating oil, and whether an emission control system is present. Many of the individual exhaust constituents remain unidentified. Appendix A contains a list ofsubstances and substance groups that have been either positively identified in diesel exhaust,detected (but not quantified in the exhaust), found in the fuel and/or lubricating oil and expectedto be emitted in the exhaust, or theorized to be present in the exhaust based on known chemicalreactions. Further research is needed to estimate many of these components contribution towhole diesel exhaust and the resulting atmospheric concentrations.
A. Diesel Exhaust's Primary Component Groups
Diesel engines operate with excess air (around 25-30 parts air to 1 part fuel: Lassiter andMilby, 1978). Consequently, the primary gaseous components of whole diesel exhaust arenitrogen (N ), oxygen (O ), carbon dioxide (CO ), and water vapor (H O).2 2 2 2
Diesel exhaust also contains substances such as carbon monoxide, oxides of nitrogen, sulfurdioxide, hydrocarbons, particulate matter, aldehydes, ketones, sulfates, cyanides, phenols, metals,and ammonia (Volkswagen, 1989). These substances are unburned fuel and lubricantcomponents, products of incomplete combustion, or are a result of engine wear or tracecontaminants in the fuel and lubricating oil.
Emissions from diesel engines have and continue to be regulated to reduce emissions ofcarbon monoxide, nitrogen oxides, sulfur oxides, hydrocarbons, and particulate matter (seeChapter IV, section D) as part of the effort to control emissions of criteria pollutants in California. Emissions of many toxic species in diesel exhaust are correspondingly being reduced as theexisting criteria pollutant standards and regulations are implemented.
B. Toxic Air Contaminants in Diesel Exhaust
Diesel exhaust contains substances formally listed as toxic air contaminants (TACs) by theState of California and as hazardous air pollutants by the U.S. EPA. Section 39655 of California'sHealth and Safety Code defines a TAC as an air pollutant which "may cause or contribute to anincrease in mortality or an increase in serious illness, or which may pose a present or potentialhazard to human health."
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Table III-1 is a list of TACs that have either been identified in diesel exhaust, or are predictedto be in diesel exhaust based on observed chemical reactions and/or their presence in the fuel orlubricating oil. Further research is needed to determine the contribution of many of thesesubstances to atmospheric diesel exhaust exposures. The exhaust constituents arsenic, benzene,and nickel are known to cause cancer in humans (IARC, 1987). These three constituents, inaddition to 1,3-butadiene, cadmium, dioxins/dibenzofurans, and formaldehyde, have been listed bythe ARB as TACs under California's air toxics identification program (Health and Safety Codesection 39660). At least 35 other diesel exhaust components and component groups wereidentified by the ARB as TACs in April 1993, under Assembly Bill (AB) 2728 (Tanner, 1992;Health and Safety Code section 39656). AB 2728 required all federally-listed hazardous airpollutants to be identified as TACs by the ARB.
C. Gas Phase Components
The composition of diesel exhaust gases is similar to that of gasoline engine gases, butbecause of the relatively higher air to fuel ratio which causes engines to have more completecombustion at increased temperatures, carbon monoxide (CO) and hydrocarbons (HC) occur inlower concentrations in diesel exhaust. However, the emissions of oxides of nitrogen (NO ), PM,x
and sulfur compounds is higher (the latter due to the higher sulfur content of the fuels).
As mentioned above, diesel exhaust is composed of both gaseous and particle phasecompounds. The gas, or vapor phase, contains typical combustion gases N , O , CO , and volatile2 2 2
hydrocarbon species (Zaebst, 1991). They include classes of compounds such asaldehydes (e.g. formaldehyde, acetaldehyde), alkanes, alkenes, and aromatic compounds (e.g. benzene, toluene, 1,3-butadiene), many of which are known or potential carcinogens.
These gas phase compounds primarily originate from the unburned fuel and lubricating oil,although some may be formed during the combustion process and by reaction with catalysts(Johnson, et al. 1994). The emissions of some of the individual organic components and classesof compounds, summarized as total hydrocarbons, have been measured by a number ofresearchers for the individual gaseous substances such as 1,3-butadiene, formaldehyde,acetaldehyde, acrolein, benzene, toluene, ethylbenzene, and xylenes (Volkswagen, 1989; Egeback& Bertilsson, 1983; Hamerle et al., 1994).
Other gas phase components of diesel exhaust, as well as other fuel combustion sources, arelow-relative molecular mass PAH and nitro-PAH derivatives (volatile 2- to 4-ring PAH and 2-ring nitro-PAH). Atmospheric reactions of these gas phase PAH and nitro-PAH derivativesmay lead to the formation of several mutagenic nitro-PAH, and nitro-PAH compounds, includingnitrodibenzopyranones, 2-nitroflouranthene and 2-nitropyrene (Atkinson and Arey, 1994;
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Table III-1Substances in Diesel Exhaust Listed by the ARB as Toxic Air Contaminants*
TACs identified under Health and Safety Code section 39660 arsenic dioxins and dibenzofuransbenzene formaldehyde1,3-butadiene nickelcadmium inorganic lead
TACs identified under Health and Safety Code section 39656acetaldehyde mercury compounds
* Further research is needed to quantify the concentrations of many of these substances before one can assess the contribution of each of these substances to atmospheric dieselexhaust exposures.
** The valence state of exhaust chromium is unknown, but a portion of total chromium emitted may be in the +VI valence state. Chromium VI is a known human carcinogen andhas been identified by the ARB as a TAC.
*** POM (polycyclic organic matter) represents a large group of compounds having at leasttwo benzene rings and a boiling point greater than or equal to 100 degrees Celsius. The PAHs (polycyclic aromatic hydrocarbons) are a subset of POM, and also represent a largenumber of compounds. Several PAHs can be converted to more potent substances in theexhaust stream or in the atmosphere. For example, benzo[a]pyrene can be converted to3-nitro-benzo[a]pyrene, a potentially powerful mutagen (Finlayson-Pitts and Pitts, 1986;IARC, 1989).
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Arey et al., 1987; Atkinson et al., 1988). It is also believed that the majority of the ambient nitro-PAH are now thought to be formed in the atmosphere from gas phase reactions of PAH of four orless rings (Atkinson and Arey, 1994).
Although the above studies provided some quantitative estimates on the compoundsmentioned, further research is needed to quantify the gaseous components of diesel exhaust froma variety of engines and test conditions before quantitative estimates of many of the gas phasecomponents can be made.
D. Particulate Matter
Diesel exhaust is characterized by a significantly higher content of particulate matter than thatof a gasoline-fueled vehicle (Volkswagon, 1989; Williams, 1989; WHO, 1996). The amount andcomposition of particles emitted from various diesel engines varies greatly, depending on factorslike engine design, load, operating speed, fuel composition, and engine emission controls. Ingeneral, newer heavy-duty trucks emit about 20 times more particulate than catalyst-equippedgasoline- fueled vehicles (WHO, 1996). However, depending on operating conditions, fuelcomposition, and engine control technology, light-duty diesel engines can emit 50 to 80 times andheavy-duty diesel engines 100 to 200 times more particulate mass than typical catalyticallyequipped gasoline engines (McClellan, 1986).
In urban areas, mobile sources are major contributors to ambient PM concentrations. 10
Several studies have demonstrated the importance of these sources (Watson et al., 1988; Chow et al., 1991; Wittorff et al., 1994; Gertler et al., 1995; Chow et al., 1996). Chow et al.(1991) looked at PM and PM source contributions in Phoenix in the winter of 1989-1990. 10 2.5
Chemical characteristics of source emissions and ambient concentrations were used as input datato the chemical mass balance (CMB) receptor model which calculates the contributions to theatmospheric PM . Results indicated that primary motor vehicles contributed up to 52 percent of10
the observed ambient PM concentrations, of which, at least 50 percent was derived from diesel10
engine exhaust. In a similar study done in Bullhead City, Arizona during 1988-1989, Gertler et al.(1995) estimated that primary motor vehicle emissions contribute a yearly average of 17 percent of the measured ambient PM concentrations. In another study, Wittorf et al. (1994)10
used the CMB receptor model to apportion the sources of ambient PM observed at a site heavily10
impacted by diesel emissions. Results showed that primary diesel exhaust emissions contributedan average of about 53 percent of the ambient PM mass observed. In a study done by Chow et10
al., (1996) in Santa Barbara, California, aerosol samples were analyzed chemically using standardmethods, and source contributions to PM were determined using the CMB model. Results10
showed that primary motor vehicle emissions were responsible for up to 42 percent of the PM mass. 10
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1. Particle Formation
Studies have shown that the primary soot particles in diesel exhaust are formed in thecombustion chamber by nucleation of heavy relative molecular weight PAH (Johnson et al.,1994), with a large percentage of these being oxidized during the expansion stroke (Luo et al.,1989). The particles that survive oxidation typically agglomerate together to form the long chainaggregates or clusters associated with diesel particles (Kittleson et al. 1985). The final particleprocesses occur in the atmosphere. These are mainly photochemical reactions and to a lesserextent particle surface reactions. It is also possible to have gas-to-particle conversion due to thenucleation of hydrocarbons, oxides of nitrogen, or oxides of sulfur (Baumgard andJohnson, 1996).
2. Particle Size Distribution
Studies have shown that the particle size distribution of diesel exhaust is bi-modal with anuclei mode (0.0075 to 0.042 Fm in diameter) and an accumulation mode (0.042 to 1.0 Fm indiameter) (Baumgard and Johnson, 1996), most of which occur in aerodynamic diameters rangingfrom 0.1 to 0.25 Fm (Groblicki and Begeman, 1979; Dolan et al., 1980; National ResearchCouncil, 1982; Williams, 1982). Approximately 98 percent of the particles emitted from dieselengines are less than 10 microns in diameter, 94 percent less than 2.5 microns in diameter, and92 percent less than 1.0 microns in diameter (see Table III-2) (ARB, 1997). The light absorbingblack portion of these particles, commonly referred to as elemental carbon (EC), is determined tobe a major contributor to reduced visibility in urban areas (Gray, 1986; Trijonis et al., 1990).
* Based on ARB 1995 emission inventory (ARB, 1997)
3. Particle Composition
The particles emitted from diesel engines are mainly aggregates of spherical carbon particlescoated with organic and inorganic substances (Figure III-1) with the composition of the particlesbeing predominantly, 80 to 90 percent, organic and inorganic carbon (Lowenthal et al., 1994). The inorganic fraction consists of small solid carbon particles, ranging from 0.01 to0.08 micrograms (McClellan, 1986), and sulfur, oxygen, carbon, sulfate (SO ), CO and NO4 x
(Johnson et al., 1994). The amount of the solid carbon, or EC, in the average particle willtypically range from approximately 64 percent (Gray, 1986) to 71 percent (Volkswagen, 1989). The fine EC aerosol is formed during the combustion process, and is not found in the atmosphere
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Figure III-1 Diesel Exhaust Particles are Mainly Aggregates of Carbon Particles
by reactions involving gaseous hydrocarbon precursors. Therefore, the entire concentration ofEC observed in the atmosphere is from primary emission sources.
The characteristic sponge-like structure and large surface area (50 to 200 m /gram of soot:2
Volkswagen, 1989) of particles emitted from diesel engines make it an excellent carrier fororganic compounds of low volatility. These compounds reside on the particle surface (as a liquid)or are included inside the particle, or both. Organic compounds present inside the particles maybe protected against photolysis and chemical reaction, while organic compounds present on thesurface of the particles can volatilize or react with other compounds from the particle surface(described in more detail in Chapter VI).
The organic fraction of the diesel particle contains compounds such as aldehydes, alkanes andalkenes, aliphatic hydrocarbons, and PAH and PAH-derivatives (Zielinska, 1990; Johnson et al.,1994). The organic fraction comes from the unburned fuel and lubricating oil (see section F), andfrom partially oxidized fuel and oil (Williams et al., 1987). The majority of the organic fraction isadsorbed onto the surface of the solid carbon core. This fraction is called the soluble organicfraction (SOF) because of its solubility in solvents such as dichloromethane (Bagely et al., 1993). Also associated with the total particle mass (TPM) of the particulate matter may be droplets ofliquid, condensed hydrocarbons, and SO particles (Johnson et al., 1994). These hydrocarbons4
collected with the TPM are not volatile enough to exist in the vapor phase and may not beadsorbed onto the solid fraction due to low solid levels, but will also be removed by an organicsolvent as the SOF (Johnson et al., 1994). The National Research Council (1983) has shown thatapproximately 25 percent of the particle mass may be extracted using organic solvents but,depending on the engine conditions and testing cycle, the contribution of organics to the TPM isbetween 10 and 90 percent (Williams et al., 1989).
The SO fraction of diesel exhaust TPM is composed primarily of the sulfuric acid formed4
when sulfur trioxide (SO ) reacts with water vapor (Truex et al., 1980). SO is formed from the3 3
oxidation of SO , which is produced during the combustion process by the oxidation of sulfur in2
the fuel (Bagely et al., 1993). This portion can contribute up to 14 percent of the diesel exhaustparticle (Lowenthal et al., 1994).
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Figure III-2Carbon is the Primary Element in a Diesel Exhaust Particle
(adapted from Volkswagen, 1989)
Recently, a study conducted by Bagely et al. (1996), characterized the physical and chemicalcomposition of emissions from a 1988 heavy-duty diesel engine equipped with a ceramicparticulate trap, and a 1991 heavy-duty diesel engine equipped with an oxidation catalyticconverter. The investigators determined the number and size of particles within the exhaust of thetwo engines tested. The results show that, despite a substantial reduction in the weight of thetotal particulate matter, the total number of particles from the more advanced 1991-model enginewas 15 to 35 times greater than the number of particles from the 1988 engine when both engineswere operated without emission control devices. This suggests that more fine particles, apotential health concern, could be formed as a result of new technologies. Further study isneeded since the extent of these findings only measured exhaust from two engines and enginetechnologies.
Finally, diesel vehicle exhaust particles yield an average composition (by weight) of carbon(88.3 percent), oxygen (4.9 percent), hydrogen (2.6 percent), sulfur (2.5 percent), metals (1.2percent) and nitrogen (0.5 percent) (Volkswagen, 1989). Figure III-2 depicts this information.
Engines running under low load typically produce fewer particles with a higher proportion oforganic compounds associated with the available particle mass. Conversely, engines under highload typically produce more particulate matter with a lower proportion of organic compoundsassociated with the available particles. Kishi et al. (1992) found that exhaust gas temperature wasan important determinant for particle composition; low exhaust gas temperatures producedparticulate matter with more adsorbed soluble organics than did particulate matter produced in a
high exhaust gas temperature environment.
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Inorganic exhaust components are products of engine and component wear, or are tracecontaminants of the fuel and/or lubricant oil. The inorganic compounds associated with theparticles are primarily trace fuel contaminants such as antimony, arsenic, barium, beryllium,cobalt, and strontium. These substances usually vaporize in the combustion chamber and then"plate" themselves to particles in the exhaust stream. Inorganic exhaust particles can also act ascondensation nuclei for vapor-phase exhaust components.
E. PAH and PAH-derivatives
Over that last 10-15 years, several researchers have investigated the health effects of PAHemissions and their atmospheric transformation products. The focus for this attention arose fromobserved mutagenic and carcinogenic effects of this important class of compounds and their nitro-derivatives. Diesel engine emissions are one of several sources of PAH and nitro-PAH emissionsfound in the ambient atmosphere. This section focuses on the PAH and PAH-derivatives found indiesel exhaust.
PAH and PAH-derivatives present in the atmosphere are distributed between the gas andparticle phases mainly due to their liquid-phase vapor pressure (Bidleman, 1988). They are mostlikely to be formed by incomplete combustion of hydrocarbons at high temperatures (Kittleson etal., 1985; Tokiwa and Ohnishi, 1986). They are also formed from the reaction of parenthydrocarbons with nitrogen oxides in ambient air. Possible sources of PAH in diesel exhaust areunburnt PAH from the fuel, electrophylic nitration of PAH during combustion, crankcase oils, andengine or systems deposits.
A wide spectrum of gas- and particle-phase PAH and PAH-derivatives are emitted in dieselexhaust (National Research Council, 1983; Jensen and Hites, 1983; Barbella et al., 1988). Manyof the PAH that can be extracted from the exhaust particle mass are unburned fuel and/orlubricant oil components (Obuchi et al., 1987; Barbella et al., 1989) like the fuel componentsnaphthalene, fluorene, phenanthrene and their alkyl derivatives (Williams et al., 1986). PAH mayalso be formed in the combustion chamber during the combustion of diesel fuel (Tancell et al.,1995).
Methylated PAH appear to be the most abundant PAH-derivatives in diesel exhaust. Schuetzle et al. (1981) identified over 100 oxy-PAH in the moderately polar fractions of a dieselexhaust extract. The extract also contained hydroxy-, ketone-, quinone-, acid anhydride-, nitro-,and carboxaldehyde-PAH-derivatives.
The nitro-PAH compounds are recognized mutagens and can be formed by the nitration ofPAH by NO in an acid environment (Pitts et al., 1979). More than 50 nitro-PAH have been2
identified in diesel exhaust, including mononitro-PAH, mononitro-alkyl-PAH, di- andtrinitro-PAH, and oxygenated nitro-PAH (Schuetzle et al., 1982; Paputa-Peck et al., 1983;Robbat et al., 1986). The major nitro-PAH observed in diesel exhaust are isomers of the parentPAH derivatives, formed by electrophilic nitration (Schuetzle, 1983; Nielsen, 1984). The mostabundant nitro-PAH in diesel exhaust are 1-nitropyrene and 2-nitrofluorene (Schuetzle and Perez,
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1983; Beje and Moller, 1988). Henderson et al. (1984) suggested that the active nitrogen oxidespecies in the exhaust stream could be a limiting factor in nitro-PAH formation.
Kittelson et al. (1985) measured concentrations of select PAH and 1-nitropyrene in thecylinder and exhaust manifold of an operating diesel engine. They observed that the PAHconcentrations were higher in the cylinder than in the exhaust manifold, but the 1-nitropyreneconcentrations were higher in the exhaust manifold than in the cylinder. This suggests that mostof the nitro-PAH in the exhaust are probably formed during the expansion/exhaust process ratherthan during combustion.
Nitro-PAH can also be formed during transport through the atmosphere by reactions ofadsorbed PAH with nitric acid, by gas-phase radical-initiated reactions in the presence of oxidesof nitrogen (Atkinson and Arey, 1994; Pitts, 1983), and the artifactual formation of nitro-PAHduring high volume sampling of ambient air (Arey et al., 1988).
In a recent study, researchers detected a new class of compounds that have direct mutagenic activity in organic extracts of both diesel exhaust and airborne particles. Specifically, 3-nitrobenzanthrone was isolated and studied. Its mutagenicity compares with that of 1,8-dinitropyrene, which is one of the strongest direct acting mutagens by Ames assay. 3-nitrobenzanthrone is formed during the combustion process of fossil fuels and from reactionbetween benzanthrone and lower oxides of nitrogen (Enya and Suziki, 1997).
F. Contribution of Lubricating Oil to Diesel Exhaust Particulate Matter
The contribution of lubricating oil to diesel exhaust PM emissions can be substantial. Researchers have reported that from 2 to 48 percent of the diesel exhaust PM mass, depending onspeed and load, consisted of material from lubricating oil. Of this material, lubricating oil cancontribute up to 88 percent of the SOF of a diesel exhaust particle (Mayer, et al., 1980; Cartillieriand Tritthart, 1984; Williams, et al, 1989; Rogge, et al., 1992). This contribution is important since several studies show that portions of the SOF of the diesel exhaust particle containssubstances which are mutagenic, carcinogenic, or both (Pierson et al., 1983; Dorie et al., 1987;Rasmussen, 1988; NIOSH, 1988; Hsieh et al., 1993).
G. Current Research on Diesel Exhaust Emissions
The 1988 ARB diesel fuel regulation which became effective October 1, 1993, mandatedreformulated diesel fuel that limited the maximum sulfur content to 0.05 percent, the minimumcetane index to 40, and the maximum aromatic content to 10 percent. Since lowering thearomatic content to levels under 10 percent would dramatically increase the production costs,ARB decided to allow alternative fuels with a higher aromatic content as long as equivalentemissions reductions could be demonstrated. The diesel fuel regulation was adopted for thepurpose of reducing particulate matter (PM) and oxides of nitrogen (NO ) (criteria pollutants),x
and was not specific to toxic components of diesel exhaust.
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To investigate the effects that diesel fuel composition may have on the toxic exhaustconstituents from diesel engines, ARB funded a study by the College of Engineering, Center forEnvironmental Research and Technology (CE-CERT) at the University of California, Riverside. The primary purpose of this study was to obtain a preliminary assessment of the potential impactof diesel fuel formulation on toxic components and on the speciation of hydrocarbons in dieselexhaust. The test was conducted on a Cummins L10 engine (represented the most-used heavy-duty diesel engine in California) operating on pre-October 1993 California diesel fuel, on fuel withlower than the 10 percent aromatic content requirement, and on a mix of alternative fuels withhigher aromatic content that comply with ARB’s regulation. Testing was conducted fromDecember 1996 to January 1997 and results became available in spring of 1998.
The results from the CE-CERT draft final report show comparable criteria pollutantreductions to those estimated in the ARB staff report for the 1988 diesel fuel regulation. The low aromatic and typical in-use fuels produced particulate matter and NO exhaust emissions thatx
met the diesel fuel regulation requirements. For more deatiled information on these and othermeasured substances, see Evaluation of Factors that Affect Diesel Exhaust Toxicity (draft finalreport), ARB Contract No. 94-312 (CE-CERT, 1998).
The contract was planned as a scoping study. It should be emphasized that the study designdid not allow the resulting data to be used to obtain statistically robust conclusions (due to use ofone engine and the limited number of data points for each target analyte/fuel combination). Inparticular, additional data would need to be collected from other types of engines and drivingconditions. Rather, the data collected was intended to be used to characterize the influence ofdiesel fuel formulation on the emissions of toxic species and to assist in the design of morecomprehensive studies.
Total Hydrocarbons (THC), NO , and Carbon Monoxide (CO)x
Emissions of THC and NO show the following order of emissions rate with fuel type: x
pre-1993 > alternative > low aromatic. The emissions rate for THC and NOx from the use of thealternative fuel was approximately six and three percent lower, respectively, than from use of thepre-1993 fuel.
The use of the low aromatic fuel resulted in an increase, and the alternative fuel in a decrease,in the CO emission rates compared to use of the pre-1993 fuel.
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PM , and PM10 2.5
The use of low aromatic and alternative formulation fuels resulted in reductions in PMemission rates of approximately 20 percent compared to use of the pre-1993 fuel, comparable towhat ARB staff predicted from implementation of our 1988 reformulated diesel fuel regulation.
More than 99 percent of the particulate mass measured fell within the PM (particulate10
matter 10 microns or less) range and greater than 95 percent in the PM (particulate matter 2.5
2.5 microns or less) range. These estimates are similar to previous estimates as already indicatedin Table III-2. The ARB emissions inventory for 1995 estimates that 98 percent of diesel exhaustPM is less than 10 microns and 94 percent is less than 2.5 microns.
The size distribution of PM and PM emissions were found to be similar among the three10 2.5
different fuels used.
Elemental and Organic Carbon, Ion, and Elemental Analysis
The low aromatic and alternative fuels exhibited lower total carbon emission rates than thepre-1993 fuel. Elemental and organic carbon dominated the composition of the particulate matterfor all fuels, representing more than 97 percent of the total identified mass. Organic carbon as apercent of total carbon is relatively constant for all three fuels and ranged from 33 to 40 percent. These numbers agree fairly well with previous estimates as discussed in section D.
Carbonyls
The use of alternative fuel resulted in similar emissions rates for the targeted carbonyls(formaldehyde, acetaldehyde, acrolein, and propionaldehyde) as from use of the pre-1993 fuel.
Speciated Hydrocarbons
Differences in emission rates among the speciated hydrocarbons were small between the pre-1993 and alternative fuel for 1,3-butadiene, benzene, toluene, ethylbenzene, o-xylene, m- & p-xylene, styrene, and naphthalene.
Particle-Phase PAHs
Many of the PAHs analyzed showed little difference in emissions rates with fuel type. However, four PAHs that ARB has identified as TACs did exhibit significant reductions in thealternative formulation blend and low-aromatic fuel compared to the pre-1993 fuel. These fourPAHs were: anthracene, benz[a]anthracene, chrysene (co-eluted with triphenylene), anddibenzo[a,h]pyrene.
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Nitro-PAHs
1-Nitropyrene, 6-nitrobenzo[a]pyrene, 9-nitroanthracene, and 1- and 2-nitronaphthalenewere measured in the emissions from all three fuel types. 1-Nitropyrene was the most abundantnitro-PAH measured and the emission rate was similar among the three fuel types.
Vapor-Phase PAHs
Of all vapor phase PAHs analyzed, naphthalene emission rates were the highest for all threefuels. A comparison of the emission profiles using three different fuels showed a similardistribution of volatile alkyl-PAHs but at significantly different emission rates. Individual alkyl-PAH emission rates showed the following order with fuel type: pre-1993 > alternative > lowaromatic. Lower emissions of volatile alkyl-PAHs may lead to a decreased potential for theatmospheric formation of highly mutagenic nitro-PAHs and nitro-PAH lactones.
Nitrosamines
The pre-1993 fuel emission rate for N-nitrosodimethylamine was similar to the alternativeformulation fuel (the low aromatic fuel was not analyzed for nitrosamines). One pre-1993 fuelemission sample and one alternative formulation fuel emission sample contained measurable levelsof N-nitrosodipropylamine. No other nitrosamines, such as N-nitrosomorpholine, were detectedin any of the samples.
Previous studies have reported nitrosamine emissions from diesel and gasoline poweredvehicles. Most of these studies have centered on emissions from catalyst equipped vehicles. N-nitrosodimethylamine has been detected from malfunctioning catalyst equipped vehicles.
Dioxins
Standardized testing procedures are not available for polychlorinated dibenzo-p-dioxins(PCDD) and polychlorinated dibenzofurans (PCDF) in engine emissions. A major objective ofthis study was to develop improved methods to collect, identify, and quantify dioxins fromengines. However, the results are qualitative only and indicate the need for further methoddevelopment. Hence, results are not presented in Table III-3.
Isomers of PCDD and PCDF were detected in the emissions from the alternative formulationblend and pre-1993 fuel. The most toxic isomers, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD),1,2,3,7,8-PCDD, and 2,3,4,7,8-PCDF were not detected in the emissions from the pre-1993 northe alternative formulation fuels.
Bioassay
Mutagenic activity was detected in the particle- and vapor-phase emissions from all fuelstested. Higher mutagenic activity was observed in both the particle phase and vapor phase
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samples collected from pre-1993 fuel than from the low aromatic and alternative formulation fuel. However, the differences are not statistically significant. The calculated emission rate for particleand vapor-phase sample mutagenic activity (reported as revertants per brake horsepower perhour) was higher in the pre-1993 fuel than the low aromatic and alternative formulated fuels. Emission samples were chemically fractionated using high performance liquid chromotography(HPLC). Nine individual fractions were collected from each fuel and these fractions were testedin the bioassay. The most mutagenic fraction for the particulate matter is in a fraction (withunidentified constituents) that differs from (is more polar than) the fractions containing the PAHsand nitro-PAHs.
N-Nitrosomorpholine <7.8 <7.8 The emission rate among the individual substances may reflect averages from multiple test cycles (two hot starts) or1
the complete test matrix [1/7(cold start) + 6/7(hot start)].
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H. References for Chapter III
Air Resources Board, 1997. Emission Inventory 1995, Technical Support Division, October 1997.
Arey, J., Zielinska, B., Atkinson, R., Winer, A.M. 1987. Polycyclic Aromatic Hydrocarbon and NitroareneConcentrationsinAmbientAirDuringaWinter-timeHighNOxEpisodeintheLosAngelesBa
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sin.AtmosphericEnvironment,21:1437-1444.
Arey J., Zeilinska, B., Atkinson, R. and A.M. Winer, 1988. Formation of Nitroarenes During Ambient High-Volume Sampling. Environ. Sci. Technol., 22, 457-462.
Atkinson, R., Arey, J., Winer, A.M., Zielinska, B., Harger, W.P., and McElroy, P.A. 1988. A Survey of Ambient Concentrations of Selected Polycyclic Aromatic Hydrocarbons (PAH) at Various Locations in California. Final Report. California Air Resources Board, Sacramento,
CA.
Atkinson R. and Arey J., 1994. Atmospheric Chemistry of Gas-Phase Polycyclic Aromatic Hydrocarbons; Formation of Atmospheric Mutagens. Environ. Health Perspect., 102, 117-126.
Bagely S.T., Gratz L.D., Leddy D.G., and J.H. Johnson, 1993. Characterization of Particle- and Vapor-Phase Organic Fraction Emissions from a Heavy-Duty Diesel Engine Equipped with a
particle Trap and Regeneration Controls. Research Report No. 56. July 1993. Health Effects Institute, Cambridge, MA..
Bagely S.T., Baumgard, K.J., Gratz, L.D., Johnson, J.H., and D.G. Leddy, 1996. Characterization of Fuel and Aftertreatment Device Effects on Diesel Emissions. Research Report No. 76.September 1996. Health Effects Institute, Cambridge , M.A..
Barbella R., Bertoli C., Ciajolo A. and A. D'Anna, 1988. Soot and Unburnt Liquid Hydrocarbon Emissions from Diesel Engines. Combust. Sci. and Tech., 59, 183-198.
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Barbella R., Ciajolo A., D'Anna A. and C. Bertoli, 1989. Effect of Fuel Aromaticity on Diesel Emissions. Combust. and Flame, 77, 267-277.
Baumgard, K.J. and Johnson, J.H. 1996. The Effect of Fuel and Engine Design on Diesel Exhaust Particle Size Distributions. SAE Technical Paper Series, #960131.
Beje B. and Moller L. 1988. 2-Nitrofluorene and Related Compounds: Prevalence and Biological Effects. Mutat. Res., 196, 177-209.
Cartillieri W. and P. Tritthart, 1984. Particulate Analysis of Light Duty Diesel Engines (IDI & DI) with Particular Reference to the Lube Oil Particulate Fraction. SAE Technical Paper No. 841395.
References for Chapter III (continued)
CE-CERT, 1998. Evaluation of Factors That Affect Diesel Exhaust Toxicity. College of Engineering - Center for Environmental Research and Technology (CE-CERT), University of
California at Riverside. ARB Contract No. 94-312.
Chow J.C., Watson J.G., Richards L.W., Haase D.L., McDada C., Dietrich D.L., Moon D., and Sloane C, 1991. The 1989-90 Phoenix Study. Volume II: Source Apportionment. DRI Document No. 8931.6F1, prepared for Arizona Department of Environmental Quality, Phoenix, AZ, by Desert Research Institute, Reno, NV.
Chow J.C., Watson J.G., Lowenthal D.H. and R.J. Countess, 1996. Sources and Chemistry of PM 10
Aerosol in Santa Barbara County, CA. Atmos. Environ., 30, No. 9., 1489-1499.
Dolan D.F., Kittelson D.B. and D.Y.H. Pui, 1980. Diesel Exhaust Particle Size Distribution Measurement Techniques. SAE Technical Paper No. 800187, SAE Trans.
Dorie D.D., Bagley S.T., Woon P.V., Leddy D.G., and J.H. Johnson, 1987. Collection and Characterization of Particulate and Gaseous-Phase Hydrocarbons in Diesel Exhaust Modified by Ceramic Particle Traps. SAE Technical Paper No. 870254.
Egeback, K.E. and Bertilsson, B.M. 1983. Chemical and Biological Characterization of ExhaustEmissions from Vehicles Fueld with Gasoline, Alcohol, LPG and Diesel. (Report No. SNV PM 1635). Solina, national Swedish Environmental Protection Board, 188 pp.
Enya, T. And Suzuki, H., 1997. 3_Nitrobenzanthron, a Powerful Bacterial Mutagen and Suspected Human Carcinogen Found in Diesel Exhaust and Airborne Particles. Environmental Science andTechnology, Vol. 31, 2772-2776.
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Finlayson-Pitts B.J. and J.N. Pitts Jr., 1986. Atmospheric Chemistry: Fundamentals and Experimental Techniques. John Wiley and Sons, Publisher. New York, New York.
Bullhead City, Arizona. Journal of Air and Waste Management Association, Vol. 45, 75-82.
Gray H.A., 1986. Control of Atmospheric Fine Primary Carbon Particle Concentrations. EQL Report 23, Environmental Quality Laboratory, California Institute of Technology, Pasadena CA.
Groblicki P.J. and C.R. Begeman, 1979. Particle Size Variation in Diesel Car Exhaust. SAE Technical Paper No. 790421.
References for Chapter III (continued)
Hammerle, R.H., Horrocks, R.W., Huthwohl, G. Ketcher, D.A., Lepperhoff, G., and Luers, B. 1994. Emissions from Current Diesel Vehicles. SAE Technical Paper Series. Society of Automotive Engineers, Warrendale, PA.
Henderson T.R., Sun J.D., Li A.P., Hanson R.L., Bechtold W.E., Harvey T.M., Shabanowitz J. andD.F. Hunt, 1984. GC/MS and MS/MS Studies of Diesel Exhaust Mutagenicity and Emissionsfrom Chemically Defined Fuels. Environ. Sci. Technol., 18, 428-434.
Hsieh D.P.H., Kado N.Y., Okamoto R., Kuzmicky P., Rathbun C. and J. Ito, 1993. Measurementand Chemical Characterization of Vapor-Phase Mutagens in Diesel Exhaust. Final ReportPrepared for the California Air Resources Board, Contract No. A032-095.
International Agency for Research on Cancer (IARC), 1987. Letter from Dr. L. K. Shuker, IARC, World Health Organization, Lyon, France, to Dr. K. Hooper, California Department of Health Services, Berkeley, CA. IARC reference number CI/75/2-S4 (87). Dated 10 April 1987.
IARC, 1989. International Agency for Research on Cancer Monographs on the Evaluation ofCarcinogenic Risks to Humans. Diesel and Gasoline Engine Exhausts and Some Nitroarenes,Monograph 46, pp. 41-57.
Jensen T.E. and R.A. Hites, 1983. Aromatic Diesel Emissions as a Function of Engine Condition.Anal. Chem., 55, 594-599.
Johnson H.J., Bagley S.T., Gratz L.D. and D.G. Leddy, 1994. A Review of Diesel ParticulateControl Technology and Emission Effects. SAE Technical Paper No. 940233.
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Kishi Y., Tohno H. and M.Ara, 1992. Characteristics and Combustibility of Particulate Matter. Reducing Emissions from Diesel Combustion, Published by the Society of Automotive Engineers, Warrendale, PA. pp. 139-146. February.
Kittelson D.B., Du C.J. and R.B. Zweidinger, 1985. Measurements of Polycyclic AromaticCompounds in the Cylinders of an Operating Diesel Engine. EPA-600/D-85/012, January.
Lassiter D.V. and T.H. Milby, 1978. Health Effects of Diesel Exhaust Emissions: A Comprehensive Literature Review, Evaluation and Research Gaps Analysis. US NTIS
PB-282-795, Washington D.C., American Mining Congress.
Luo L., Pipho, M.J., Ambs, J.L., and Kittleson, D.B. 1989. Particle Growth and Oxidation in a direct-injection Diesel Engine. SAE Technical Paper No. 890580. Society of Automotive Engineers, Warrendale, PA.
Mayer J.M., Lechman D.E. and D.L. Hilden, 1980. The Contribution of Engine Oil to Diesel Exhaust Particulate Emissions. SAE Technical Paper No. 800256.
McClellan R.O., 1986. Health Effects of Diesel Exhaust: A Case Study in Risk Assessment. Amer. Ind. Hyg. Assoc. J., 47(I):1-13, January.
National Institute of Occupational Safety and Health (NIOSH), 1988. Current Intelligence Bulletin No. 50: Carcinogenic Effects of Exposure to Diesel Exhaust. DHHS Pub. No. 88-116. Gov. Printing Office, Washington, D.C.
National Research Council (NRC), 1982. Diesel Cars: Benefits, Risks, and Public Policy. DieselImpacts Study Committee, National Research Council, National Academy Press, Washington,D.C., pp. 142.
NRC, 1983. Polycyclic Aromatic Hydrocarbons: Evaluation Sources and Effects. The Committee onPyrene and Selected Analogues, National Research Council, National Academy Press,Washington, D.C.
Obuchi A., Ohi A., Aoyama H. and H. Ohuchi, 1987. Evaluation of gaseous and particle emissioncharacteristics of a single cylinder diesel engine. Combustion and Flame,
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70, 215-224.
Paputa-Peck M.C., Marano R.S., Schuetzle D., Riley T.L., Hampton C.V., Prater T.J., Skewes L.M., Jensen T.E., Ruehle P.H., Bosch L.C. and W.P. Duncan, 1983. Determination ofNitrated Polynuclear Aromatic Hydrocarbons in Particulate Extracts by Capillary Column GasChromatography with Nitrogen Selective Detection. Anal. Chem., 55, 1946-1954.
Pierson W.R., Gorse R.A. Jr., Szkariat A.C., Brachaczek W.W., Japar S.M., Lee F.S., Zweidinger R.B. and L.D. Claxton, 1983. Mutagenicity and Chemical Characteristics of Carbonaceous Particulate Matter from Vehicles on the Road. Environ. Sci. Technol., 17, 31-44.
Pitts J.N., Jr., Van Cauwenberghe K.A., Grosjean D., Schmid J.P., Fitz D.R., Belser W.L., Krudson G.B. and Hynds P.M., 1979. Atmospheric Reactions of Polycyclic Aromatic Hydrocarbons: Facile Formations of Mutagenic Nitro Derivatives. Science, 202:515-519.
References for Chapter III (continued)
Pitts J.N., Jr., 1983. Formation and Fate of Gaseous and Particulate Mutagens and Carcinogens inReal and Simulated Atmospheres. Environ. Health Perspect., 47, 115-140.
Rasmussen R.E., 1988. Genotoxicity of Diesel Exhaust Particles and Vapors Collected fromEngines With and Without Particle Trap Oxidizers. Final Report, California Air Resources BoardContract No. A5-130-33.
Robbat A. Jr., Corso N.P., Doherty P.J. and M.H. Wolf, 1986. Gas ChromatographicChemiluminescent Detection and Evaluation of Predictive Models for Identifying NitratedPolycyclic Aromatic Hydrocarbons in a Diesel Fuel Particulate Extract. Anal. Chem., 58, 2087-2084.
Rogge R.F., Hildemann L.M., Mazurek M.A. and G.R. Cass, 1992. Sources of Fine Organic Aerosol: 2. Noncatalyst and Catalyst-Equipped Automobiles and Heavy-Duty DieselTrucks. California Institute of Technology.
Schuetzle D., Lee F.S., Prater T.J. and S.B. Tejada, 1981. The identification of polynucleararomatic hydrocarbon (PAH) derivatives in mutagenic fractions of diesel particulate extracts.Intern. J. Environ. Anal. Chem., 9, 93-144.
Schuetzle D., Riley T.L., Prater T.J., Harvey T.M. and D. F. Hunt, 1982. Analysis of NitratedPolycyclic Aromatic Hydrocarbons in Diesel Particulates. Anal. Chem., 54, 265-271.
Schuetzle D., 1983. Sampling of Vehicle Emissions for Chemical Analysis and Biological Testing.Environ. Health Perspec., 47, 65-80.
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Schuetzle D. and J.M. Perez, 1983. Factors Influencing the Emissions of Nitrated PolynuclearAromatic Hydrocarbons (Nitro-PAH) from Diesel Engines. Air Poll. Cont. Assoc. J., 33, 751-755.
Tancell P.J., Rhead M.M., Pemberton R.D. and J. Braven, 1995. Survival of Polycyclic AromaticHydrocarbons during Diesel Combustion. Environ. Sci. Technol., 29, 2871-1876.
Tokiwa, H. And Ohnishi, Y. 1986. Mutagenicity and Carcinogenicity of Nitroarenes, and TheirSources in the Environment. CRC Critical Review Toxicology, 17:23-60.
Trijonis, J.C.; Malm, W.C.; Pitchford, M.; White, W.H.; Charlson, R. and Husar, R. 1990. AcidDeposition: State of Science and Technology. NAPAP report 24: Visibility Existing andHistorical Conditions-Causes and Effects. National Acid Precipitation Assessment Program.
Truex, T.J., Pierson, W.R., and D.F. McKee, 1980. Sulfate in Diesel Exhaust. Environ. Sci. Tech.14:1118.
References for Chapter III (continued)
Volkswagen, 1989. Unregulated Motor Vehicle Exhaust Gas Components. Volkswagen AG, Research and Development (Physico-Chemical Metrology). Project Coordinator: Dr. K.-H. Lies. 3180 Wolfsburg 1, F.R. Germany.
Watson J.G., Chow J.C., Richards L.W., Anderson S.R., Houck J.E. and D.L., Dietrich, 1988. The1987-88 Metro Denver Brown Cloud Air Pollution Study, Volume III: Data Interpretation. Desert Research Institute Document No. 8819.1F3, prepared for the Greater Denver Chamber ofCommerce, Denver, CO.
Williams R.L., 1982. Diesel Particulate Emissions. Toxicological Effects of Emissions from DieselEngines. J. Lewtas (Ed.), Elsevier Science Publishing Co., Inc., New York, NY, pp. 15-32.
Williams P.T., Bartle K.D. and G.E. Andrews, 1986. The Relation between Polycyclic AromaticCompounds in Diesel Fuels and Exhaust Particulates. Fuel, 65, 1150-1158.
Williams P.T., Andrews G.E. and K.D. Bartle, 1987. The Role of Lubricating Oil in DieselParticulate and Particulate PAH Emissions. SAE Technical Paper No. 87084. Society ofAutomotive Engineers, Warrendale, PA.
Williams D.J., Milne J.W., Quigley S.M., Roberts D.B. and M.C. Kimberlee, 1989. ParticulateEmissions from "In-Use" Motor Vehicles-II. Diesel Vehicles. Atmos. Environ., 23, No. 12,2647-2661.
Wittorff D.N., Gertler A.W., Chow J.C., Barnard W.R. and H.A. Jongedyk. 1994. The Impact ofDiesel Particulate Emissions on Ambient Particulate Coatings. Desert Research Institute,Presented at the 87th Annual AWMA Meeting and Exhibition, Cincinnati, Ohio,
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June 19-24, 1994.
WHO, 1996. Diesel Fuel and Exhaust Emissions. International Program on Chemical Safety. WorldHealth Organization, Geneva, 1996.
Zaebst D.D., Clapp D.E., Blade L.M., Marlow D.A., Steenland K., Hornung R.W., Scheutzle D. andJ. Butler, 1991. “Quantitative Determination of Trucking Industry Workers’ Exposures to DieselExhaust Particles.” Am. Ind. Hyg. Assoc. J., 52(12), 529-541, December.
Zielinska B., 1990. Private Correspondence. Risk Assessment of Diesel Exhaust: 1990 and Beyond,Los Angeles, California. Sponsored by the California Air Resources Board, Sacramento, CA.
Diesel engines are used to power passenger cars, trucks, buses, ships, railway locomotives, innonroad equipment used for farming and construction, and in almost every kind of industry.
A. Production
The combustion of diesel fuel in an internal combustion engine produces diesel exhaust. Approximately 2.1 billion gallons of diesel fuel were burned in internal combustion engines inCalifornia during 1995 (BOE, 1996). The State predicts that diesel fuel use will increase inCalifornia from current levels up to 2.3 billion gallons in 2000 and 2.9 billion gallons in 2010(CEC, 1998).
B. Uses
The staff is not aware of any commercial or industrial use of diesel exhaust in California. Small amounts are used in research.
C. Emissions
Diesel engine emissions have changed dramatically over the last 20 years because ofimprovements in engine technology, emissions controls, and fuel formulation. Emissions ofNO and PM are significantly lower than those from older uncontrolled engines. Emissions ofx 10
reactive organic gases (ROG) and CO have also declined as a result of engine emissionsstandards.
In this report, diesel exhaust PM emissions and air concentration estimates are used to10
represent exposure to diesel exhaust. The total emissions of toxic diesel exhaust species have notbeen estimated because inadequate analytical methods, in conjunction with excessive costs,prevent the detection and quantification of the many individual toxic and potentially toxic speciesand their atmospheric contribution. Diesel exhaust particulate matter is extremely fine (over90 percent of the particles are smaller than 1 micrometer [Fm] in diameter), readily respirable, andis the primary carrier for many of the hydrocarbons and metals found in the exhaust, many ofwhich are known or suspected mutagens and carcinogens. Because the 1990 year emissions inventory is used in our ambient concentrations analysis (see Chapter V), theprimary focus will be on the 1990 emissions inventory. We have, however, included emissionsestimates for 1995 to indicate the decrease in emissions that have occurred as a result of recentdiesel regulations and estimates of the future trends in diesel engine emissions.
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Three major source categories emit diesel exhaust in California: mobile sources (on-roadvehicles and other mobile sources), stationary area sources, and stationary point sources. Table IV-1 through Table IV-6 breaks the three major source categories into individual emissiongroups, and lists the individual groups' emissions in tons per year (TPY), both for base year 1990(inventory year used for ambient exposure analysis) and for year 1995 for diesel exhaust PM ,10
Figure IV-1 illustrates that on-road mobile sources (heavy-duty trucks, light-duty passengercars and trucks, and urban buses) emit the majority, or about 58 percent of the diesel exhaust PM10
in California for 1995. Other mobile sources contribute about 37 percent, and stationary sourcesemit about 5 percent.
Fuel combustion sources include those sources that use various fuels (e.g. solid-liquidcombustion material, gasoline, diesel fuel, natural gas, jet fuel, wood and waste combustion) intheir production or use. These sources include stationary sources such as oil and gas productionfacilities, electric utilities, and manufacturing/industrial plants, and mobile sources such as motorvehicles, ships, trains, and aircraft. Figure IV-2 illustrates that diesel exhaust PM contributes10
approximately 26 percent of the total statewide PM from fuel combustion sources. The10
The ARB staff also estimates that emissions from diesel exhaust contribute about 3 and 8percent of the total PM and PM inventories, respectively (ARB, 1997b). Diesel exhaust10 2.5
particulate matter is a larger percentage of the Statewide PM inventory, primarily because the2.5
PM inventory targets smaller particles emitted from combustion sources (see Figures IV-3 and2.5
IV-4). For both PM and PM inventories, emissions from non-diesel mobile on-road sources10 2.5
include gasoline-powered vehicles, tire wear, and brake dust; non-diesel other mobile emissionsinclude sources such as trains, ships, and mobile equipment; and non-diesel stationary (point andarea) emissions include sources such as petroleum refining, mineral processes, residential fuelcombustion, farming operations, construction and demolition, entrained road dust, and fugitivewindblown dust (ARB, 1998a,b).
1. Mobile Sourcesa. On-Road Vehicles
Heavy-duty trucks, urban buses, passenger cars, and light-duty trucks emitted an estimated27,250 tons (approximately 64 percent of the total emissions) of diesel exhaust PM statewide10
during 1990 (ARB, 1998a). Emissions from on-road vehicles has declined to 15,680 tons(approximately 58 percent of the total emissions) in 1995 due to engine emission standards and theintroduction of reformulated diesel fuel (see Table IV-1).
b. Other Mobile SourcesOther diesel-fueled mobile sources emitted an estimated 13,810 tons of engine exhaust PM10
(approximately 33 percent of the total) statewide during 1990 and 9,820 tons (approximately 37 percent of the total) in 1995. This category includes off-road transportation equipment andmobile industrial equipment such as construction and road equipment, mobile refrigeration units,ships, heavy-duty farm equipment, trains, and recreational and commercial boats (ARB, 1998a).
2. Stationary SourcesStationary sources emitted an estimated 1,364 tons of diesel exhaust PM statewide during10
1990 (approximately 3 percent of the total) and 1,400 tons (approximately 5 percent of the total)in 1995 (ARB, 1998a).
Most districts in California do not have a complete inventory of their stationary diesel engines. Consequently, the statewide emissions of diesel exhaust PM from stationary sources are likely10
higher than those reported here (which are based on available emission inventories).
a. Stationary Area SourcesStationary area sources of diesel exhaust include shipyards, warehouses, heavy equipment
repair yards, and oil and gas production operations where exhaust emissions are emitted frommultiple locations within the site. Stationary area sources emitted an estimated 1,360 and 1,370tons of diesel exhaust PM in California during 1990 and 1995, respectively (ARB, 1998a). 10
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Figure IV-31995 Statewide PM Emissions10
Figure IV-41995 Statewide PM Emissions2.5
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Figure IV-5Diesel Exhaust Mobile Source Emissions and
Projections(1990 - 2010)
b. Stationary Point SourcesStationary point sources generate diesel exhaust emissions from specific, fixed locations.
These sources include chemical manufacturing, stone, clay, and glass manufacturing, mining, publicadministration, and utility and water services. Stationary point sources emitted an estimated 4 and30 tons of diesel exhaust PM in California during 1990 and 1995, respectively (ARB, 1998a).10
D. Emission Projections
1. Mobile SourcesThere have been significant advances in the development of technology to control diesel
particulate matter emissions. Some of these efforts included engine design modifications, the useof aftertreatment devices, and improvements in fuel formulations. All of these improvedtechnologies were developed to comply with engine emission standards and fuel modifications adopted to date by ARB and the U.S. EPA. Figure IV-5 illustrates emission estimates for PM ,10
NO , and SO for the years 1990 and 1995, and emissions projections for years 2000 and 2010.x x
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Emissions of diesel exhaust PM from mobile sources in California are expected to decrease10
about 60 percent from 1990 to 2010 as a result of mobile source emission standards and regulations already adopted by the ARB and the U.S. EPA through 1997.
The use of low sulfur fuel (0.05% by mass) has led to additional reductions in total particulatematter levels of diesel exhaust. Since 1990, sulfur oxide (SO ) emissions from diesel-fueledx
vehicles have decreased about 60 percent due to the use of this fuel (sold beginning October1993). However, from now until 2010, SO emissions are expected to increase slowly due tox
increases in population, traffic congestion, and VMT.
Nitrogen oxides (NO ) emissions from diesel powered mobile sources are expected tox
decrease from now until about 2010. The U.S. EPA is proposing a new NO heavy-duty enginex
emission standard to be implemented in 2004 which will cut emissions of NO from diesel enginesx
statewide by about 18 percent each year thereafter.
a. Particulate MatterIn order to address particulate matter pollution, the U.S. EPA and the ARB have established
ambient air quality standards for PM (U.S. EPA: 24-hr - 150 Fg/m , annual arithmetic mean -103
50 Fg/m ; ARB: 24-hr - 50 Fg/m , annual geometric mean - 30 Fg/m ). The U.S. EPA has also3 3 3
adopted a new National Ambient Air Quality Standard for PM to address concerns regarding the2.5
health effects of fine particles. On July 18, 1997, the U.S. EPA adopted an annual PM standard2.5
of 15 Fg/m and a 24-hour standard of 65 Fg/m . To assist in meeting these standards, the ARB3 3
and the U.S. EPA are addressing diesel exhaust PM emissions through a series of on-road and10
other mobile source emission standards and regulations. The diesel exhaust PM standards and10
regulations for on-road and other mobile sources adopted by the ARB and the U.S. EPA include:
On-Road Mobile Sources
L emission standards that limit the gram per mile (g/mi) of PM that can be emitted from1982 and newer light- and medium-duty on-road diesel vehicles (1985: 0.4 g/mi;1986-88: 0.2 g/mi; and 1989 and newer: 0.08 g/mi.);
L PM emission standards for 1988, 1991, and 1994 and newer diesel powered heavy-dutyvehicles of 0.60, 0.25, and 0.10 grams per brake-horsepower-hour (g/bhp-hr),respectively, except for urban bases;
L PM emission standards that limit new 1991 through 1993 urban bus engines fromemitting more than 0.10 g/bhp-hr. 1994-1995 model year urban bus engines are requiredto meet a 0.07 g/bhp-hr interim in-use standard. Beginning in 1996, new urban buses arerestricted from emitting more than 0.05 g/bhp-hr;
L the roadside testing of heavy-duty on-road vehicles for excessive smoke opacity (1991);
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L use of low sulfur/low aromatics diesel fuel (October 1993) that helps reduce PMemissions from mobile sources (excluding locomotives and marine vessels);
L continuation of the fleet inspection and maintenance program for heavy-duty vehicles(anticipated implementation in early 1998);
Other Mobile Sources
L PM emission standards for 1995 and newer utility diesel engines rated under 25 horsepower (1995-98: 0.9 g/bhp-hr; 1999 and newer: 0.25 g/bhp-hr);
L hydrocarbon (HC) + NO emission standards for 1995 and newer utility diesel engines x
rated under 25 horsepower (1995-98: 12.0 g/bhp-hr for engines less than 225 cubiccentimeters (cc) and 10.0 g/bhp-hr for engines greater than or equal to 225 cc; 1999 andnewer: 3.2 g/bhp-hr for all engines under 25 horsepower);
L PM emission standards for certain heavy-duty off-road diesel engines rated from 175 to750 horsepower (1996-2000: 0.4 g/bhp-hr; 2001 and newer: 0.16 g/bhp-hr);
L NO emission standards for certain heavy-duty off-road diesel engines rated from 175 tox
750 horsepower (1996-2000: 6.9 g/bhp-hr; 2001 and newer: 5.8 g/bhp-hr);
L PM emission standards for certain heavy-duty off-road diesel engines rated above 750 horsepower (2000 and newer: 0.4 g/bhp-hr); and
L NO emission standards for certain heavy-duty off-road diesel engines rated above x
750 horsepower (2000 and newer: 6.9 g/bhp-hr).
As a result of these control measures, statewide diesel exhaust PM emissions from on-road10
diesel vehicles are expected to be reduced by approximately 80 percent over the period 1990-2010(Figure IV-6). The expected reduction is due to adopted diesel vehicle emission and fuelregulations (listed above), even though both the number and VMT of heavy-duty trucks areexpected to increase substantially during this period.
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Figure IV-6Diesel Exhaust On-Road Vehicle
PM Emissions Projections10
b. Sulfur OxidesSulfur is a component of diesel fuel, and is emitted in diesel exhaust as sulfur oxides.
Approximately 98 percent of the sulfur is emitted as sulfur dioxide (SO ) and 2 percent of2
particulate sulfate (Pierson et al., 1978; Truex et al., 1980). Sulfur oxide (SO ) inhalation canx
cause bronchial tube constriction and exacerbation of preexisting respiratory or pulmonary disease(Blumenthal, 1985). Additionally, SO emissions from diesel-fueled engines, which may undergox
chemical reactions in the atmosphere to form acidic sulfates, can contribute to acid deposition inCalifornia. The principle chemical transformation of SO in the atmosphere is reaction with the2
OH radical followed by the formation of sulfuric acid (Stockwell and Calvert, 1983). SO mayx
also react with other compounds in the atmosphere to form particles which contribute to PMemissions.
Since October 1993, diesel fuel sold in California for combustion in mobile sources (excludinglocomotives and marine vessels) has been reformulated to be a low aromatic/low sulfur diesel fuel. Use of this reformulated fuel has resulted in lower emissions of SO , NO and PM, and lowerx x
ambient air concentrations of SO in areas impacted by diesel exhaust emissions. Low sulfur dieselx
fuel has been required in the South Coast Air Basin since 1985.
Statewide SO emissions from on-road diesel vehicles are expected to have decreased byx
about 64 percent from 1990 to 1995, and increase slowly after that due to growth in vehicles andVMT (see Figure IV-7).
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Figure IV-7Diesel Exhaust On-Road Vehicle
SO Emissions Projectionsx
c. Nitrogen OxidesDiesel engines produce nitrogen oxides (NO , primarily nitrogen monoxide) as a result of ax
high-temperature combustion process that uses large amounts of air. NO is the sum of nitricx
oxide (NO), nitrogen dioxide (NO ), and other nitrogen oxide components. This makes2
controlling both NO and particulate matter emissions for a diesel engine difficult, because thex
decrease of one usually results in the production of the other. NO inhalation can causex
constriction of the bronchial tubes, exacerbation of preexisting lung disease, and an increasedsusceptibility to respiratory infections (Blumenthal, 1985). Additionally, NO emissions fromx
diesel-fueled engines contribute to acid deposition and tropospheric ozone formation.
Diesel exhaust contains mutagenic substances that are a result of NO radical reaction. Forx
example, the major nitro-PAHs observed in diesel exhaust are formed by electrophilic reaction ofthe parent PAHs with NO radicals (see Chapter III). A reduction in the amount of NO in thex x
exhaust stream should result in lower exhaust pipe/stack emissions of mutagenic nitro-compounds.
Since 1991, new heavy-duty diesel trucks and buses in California have been restricted fromemitting more than 5.0 grams of NO per brake horsepower hour (g/bhp-h). As a result of the x
diesel fuel regulations adopted by the ARB in 1993, NO emissions from diesel-powered motorx
vehicles have reduced NO emissions by about 7 percent (70 tons per day). In 1996, the NOx x
standard for new heavy-duty urban buses became 4.0 g/bhp-h. In 1998, new heavy-duty truckswill be required to meet the same standard. In addition, and as part of California’s plan to addressheavy-duty diesel vehicle pollutants, the U.S. EPA, ARB, and the leading manufacturers
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Figure IV-8Diesel Exhaust On-Road Vehicle
NO Emissions Projectionsx
of heavy-duty diesel engines signed a historical agreement to reduce emissions of NO andx
hydrocarbons. In this “Statement of Principles,” signed on July 11, 1995, the signatories agreed topursue new heavy-duty diesel engine standards from future trucks and buses on a nationwide basisby proposing a national non-methane hydrocarbon (NMHC) plus NO standard of 2.4 g/bhp-hr, orx
a combined NMHC plus NO standard of 2.5 g/bhp-hr with an NMHC cap of 0.5 g/bhp-hr. Thex
U.S. EPA formally proposed these standards in a Notice of Proposed Rulemaking on June 2, 1996. The final rule was published in the Federal Register in October 1997. The newstandards are proposed to be implemented beginning in 2004, and are predicted to decrease NOx
emissions by approximately 71 tons per year or about 18 percent. The ARB staff is proposing toadopt a similar emission standard at a ARB public hearing in April 1998.
Lower emissions of NO from affected sources will result in lower ambient air concentrationsx
of NO in areas impacted by diesel exhaust emissions. Since NO is an ozone precursor, this wouldx x
decrease the amount of ozone formed in the atmosphere.
As a result of the regulations mentioned above, the ARB projects that statewide NOx
emissions from on-road diesel vehicles will decrease by about 19 percent from now until 2010(Figure IV-8).
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2. Stationary SourcesDiesel exhaust emissions from stationary sources are increasing with the increase in
California's population. Emission regulations that will slow the increase in diesel exhaust PM andNO emissions from these types of sources have been addressed or may be addressed by the localx
air pollution control districts.
E. Indoor Sources of Diesel Exhaust
Indoor non-occupational environments will not typically have sources of indoor dieselexhaust. The presence of diesel exhaust indoors will normally result from infiltration of outdoorair contaminated with diesel exhaust. Industrial workplaces such as fire stations and loading docksare potential sources of indoor exposures. These environments may have occasional indoorsources such as diesel-powered tools, machinery, forklifts, and vehicles. Such sources may beused in enclosed work spaces near outdoor air intakes that draw the exhaust in and deliver it toindoor work spaces. Exposure to diesel exhaust indoors is discussed in more detail in Chapter V.
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F. References for Chapter IV
ARB, 1997a. Emission Inventory. Run Date: 12/31/97. Technical Support Division, Air Resources Board.
ARB, 1997b. Emission Inventory. Run Date: 7/2/97. Technical Support Division, Air Resources Board.
ARB, 1998a. Emission Inventory. Run Date: 1/2/98. Technical Support Division, Air Resources Board
ARB, 1998b. Emission Inventory. Run Date: 4/29/98. Technical Support Division, Air
Resources Board
ARB, 1998c. Emission Inventory. Run Date: 1/5/98. Technical Support Division, Air Resources Board
BOE, 1996. Data obtained from the California Board of Equalization. Use Fuel: Total DieselGallonage for Year 1995. Run Date: 10/29/96. Board of Equalization, Legislative Division,Sacramento, CA.
Blumenthal D.S., M.D., 1985. Introduction to Environmental Health. Springer PublishingCompany, Inc., New York, New York. ISBN 0-8261-3900-0.
CEC, 1998. Data obtained from the California Energy Commission (CEC). Draft fuel consumption projections. Energy Information and Analysis Division, Sacramento, CA.
Pierson W.R., Brachaczek W.W., Hammerle R.H., McKee D.E. and J.W. Butler, 1978. SulfateEmissions from Vehicles on the Road. J. Air Pollut. Control Assoc. 28, 123-132.
Stockwell, W.R. and Calvert, J.G., 1983. The Mechanisms of the HO-SO Reaction. Atmosheric2
Environment, Vol. 28, 3,083-3,091.
Truex T.J., Pierson W.R., and D.F. McKee, 1980. Sulfate in Diesel Exhaust. Environ. Sci. Tech.14:1118.
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V.EXPOSURE TO DIESEL EXHAUST
The main focus of this chapter is to provide an estimate of near source and total exposure todiesel exhaust PM in California. It also includes: a discussion of monitoring methods used by10
other researchers to predict ambient concentrations of diesel exhaust PM , a description of ARB’s10
method for estimating outdoor ambient concentrations, ARB staff projections for future ambientdiesel exhaust PM concentrations, an estimate of indoor exposures, and a discussion of other10
routes of exposure (multipathway).
A. Monitoring for Diesel Exhaust
Diesel exhaust is a complex mixture of thousands of gases and particles. Because of itscomplex mixture and that many of the individual constituents of diesel exhaust may be emitted from other combustion sources, whole diesel exhaust has not been directly monitored or quantifiedin the atmosphere.
The most common approach to monitoring diesel exhaust has been to select a surrogatemeasure or measures of exposure that are representative of the exhaust as a whole. Althoughdiesel exhaust markers (substances unique to diesel exhaust that could be used to qualify andquantify its presence in the atmosphere) have not been found, fine particles and elemental carbonhave been used as surrogates of exposure to diesel exhaust particulate matter. Consequently, ambient diesel exhaust PM concentrations are often used by researchers to represent the public'sexposure to whole diesel exhaust.
The ARB staff estimated diesel exhaust concentrations using a PM-based exposure method. Although there are several diesel exhaust PM estimation methods (discussed on following pages),the staff of the ARB used a PM-based exposure estimation method for the following reasons:
< we have a comprehensive emissions inventory and ambient concentrations data base fordiesel exhaust-derived PM in California;
< diesel exhaust PM contains many of the toxic components of the exhaust; and
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< diesel exhaust PM has been shown to contribute a significant portion of the exposure tothe whole exhaust. The PM has been associated with approximately 50 (Hsieh et al.,1993) to 90 (Schuetzle, 1983) percent of the mutagenic potency of whole diesel exhaust, (NIOSH, 1988)*.
Toxic gas-phase exhaust constituents like acetaldehyde, benzene, 1,3-butadiene, andformaldehyde are not directly included in a PM-based exposure estimation because they are nottypically carried on or in the particles. The ARB and others have initiated research to improve andrefine the estimates of exposure to the gas-phase portion of the exhaust.
Until more sophisticated estimation methods can be devised, PM-based estimation methodsprovide a useful tool to develop diesel exhaust exposure estimates.
Table V-1, adapted from Krieger et al. (1994), lists ambient diesel exhaust PM concentrationestimates developed by a number of researchers using a variety of data bases and estimationmethods. Most of the estimations presented in the Table are not California-specific, and representonly general diesel exhaust PM air concentrations (California-specific data are presented later inthis Chapter). Based on the information shown in Table V-1, ambient diesel exhaust PMconcentrations range from 0.2 to 23 Fg/m . 3
As discussed, several diesel exhaust PM estimation methods have been developed. Theseinclude the use of the following:
1. TracersAlthough diesel exhaust may not contain markers that can be used to qualify and quantify its
presence in the atmosphere, it does contain substances predominately emitted from diesel-fueledengines (tracers) which can be used to estimate its presence and concentrations. Tracer substancesare consistently emitted from diesel-fueled engines, and can be consistently monitored in the air. Diesel exhaust tracers that have been suggested by various researchers include particle-associateddiesel fuel additives, elemental carbon, PAH and PAH ratios, and lubricating oil combustionproducts. Known quantities of substances not normally found in the atmosphere can also be addedto the fuel as artificial tracers.
In an effort to quantify atmospheric concentrations of diesel exhaust in Vienna, Austria,researchers added a small amount of the rare element dysprosium to the area's entire diesel fuelsupply. Dysprosium is not normally detected in ambient air, and its quantifiable presence inVienna's atmosphere during the 4-week study period allowed scientists to successfully qualifyand quantify its carrier (diesel exhaust PM) in the atmosphere through PM sampling and analysis.--------------------------------* The OEHHA's discussion and evaluation of diesel exhaust's toxicity is contained in the
Part B Health Risk Assessment for Diesel Exhaust.
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Table V-1Estimates of Diesel Exhaust Ambient PM Concentrations by
Selected Researchers
Conditions/Method for Year Concentrations (Fg/m ) Reference3
Ambient Concentration Estimates Using:
Dysprosium Tracer - range 1988 5 - 23 Horvath, et al., 1988 - typical 1988 11
Lead Surrogate - range 1995 0.7 - 3.9 U.S. EPA, 1983
Elemental Carbon - range 1982 3.4 - 5.7 Adapted from Surrogate Denton, et al., 1992
NAAQS Exposure Model - range 1995 3.1 - 3.7 U.S. EPA, 1983 NAAQS Exposure Model modified 1986 2.6 Ingalls, 1985
Source Apportionment - Urban Areas 1991 4 - 22 Chow et al. 1991
Horvath et al. (1988) found that from 12 to 33 percent of the PM suspended in Vienna'satmosphere was diesel exhaust PM, in concentrations that varied with the density and flow oftraffic. The diesel exhaust PM mixed well in the atmosphere, and there were no dramaticdifferences in ambient concentrations between busy commercial areas and calm residential areas. Diesel exhaust PM concentrations during the study ranged between 5 and 23 Fg/m , with typical3
concentrations around 11 Fg/m . The researchers observed that the diesel exhaust PM3
concentrations increased 5.5 Fg/m above ambient levels for every 500 diesel-fueled vehicles3
passing near a monitoring site per hour.
2. Modeled Exhaust EmissionsResearchers at Volkswagen (1989) estimated air concentrations of vehicle exhaust PM in
urban street canyons and near U.S. expressways. The researchers used emission factors foron-road gasoline- and diesel-fueled vehicles, estimates of the numbers and types of vehicles on theroad, diurnal activity patterns, and mathematical simulation models of a typical U.S. street canyonand expressway. Emissions from heavy-duty on-road vehicles were not included in the researchers'calculations.
The researchers estimated that vehicle exhaust PM concentrations in the street canyon wouldrange from 3.9 to 8.8 Fg/m , while PM concentrations near the expressway would range from 7.143
Fg/m at 4 meters from the side of the road, to 2.57 Fg/m at 100 meters from the side of the road. 3 3
3. Source ApportionmentSource apportionment is a technique for identifying the sources and source emissions which
contribute to the total ambient air concentrations of a pollutant in a specific area. PM sourceapportionment typically employs a chemical mass balance (CMB) model to match the chemicalprofiles of ambient PM samples with known chemical profiles of PM from specific types ofsources. Source apportionment can be used to calculate diesel exhaust PM concentrations in aspecific area for which adequate emissions inventory and PM ambient air data are available. Withthis information, future year diesel exhaust PM concentrations can be estimated from future yearemission inventories (see section D).
a. PM Source Apportionment10
Zielinska (1991) reported that a PM source apportionment study conducted by the Desert10
Research Institute during the winter of 1989-1990 (Chow et al., 1991) produced estimates ofmotor vehicle exhaust concentrations for West Phoenix, Central Phoenix, and South Scottsdale,Arizona. The results of this study indicated that primary motor vehicle exhaust is the secondhighest contributor to PM at all sampling sites, and that diesel-fueled motor vehicle exhaust was10
determined to be responsible for at least half of the motor vehicle-derived PM .10
The calculated diesel exhaust PM concentrations for the winter study period ranged from10
approximately 4 Fg/m (at all three sites), to 14 Fg/m (in South Scottsdale) and 22 Fg/m (in3 3 3
Central Phoenix).
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b. Elemental Carbon Source ApportionmentAs previously mentioned, elemental carbon (EC) has been used by researchers to estimate
ambient diesel exhaust PM concentrations. Gray (1986) used fine particulate EC ambient data(particle sizes below 2.1 in diameter) collected in the Los Angeles area in 1982 and emissionsinventory data to determine source contributions from diesel engine emissions. Results indicatedthat diesel engine emissions were responsible for approximately 67 percent of the fine EC mass inthe Los Angeles area atmosphere, and that the exhaust particles averaged about 64 percent EC. Average annual fine EC concentrations ranged from 3.03 to 5.04 Fg/m . From this information,3
we derived approximate concentrations of fine PM attributed to diesel exhaust by multiplying theEC concentrations measured during the study by 67 percent and dividing the result by 64 percent. In addition, Gray estimates that the fine PM constitutes about 93 percent of the PM mass for10
diesel emissions. This percentage is then divided by the fine diesel exhaust PM concentration todetermine total diesel exhaust PM concentrations. Therefore, diesel exhaust PM concentrations,10
calculated as described above, ranged from approximately 3.4 to 5.7 Fg/m (See Table V-1).3
In another study, diesel exhaust PM concentrations were estimated in the South Coast from10
ambient PM measurements taken throughout 1986 and source apportioned using the CMB model10
(Gray et al., 1989; reported in 1991). The results of the study indicate the following: The averagediesel exhaust PM concentrations due to light-duty diesel emissions ranged from 3.6 to 5.6 Fg/m3
across the eight sites in the study area (averaging 4.6 Fg/m ). The highest average 3
24-hour diesel exhaust PM concentrations in the study area ranged from 6.2 to 22.0 Fg/m3
(averaging 14.3 Fg/m ). 3
B. ARB Staff Method for Estimating Diesel Exhaust PM Outdoor 10
Ambient Concentrations in California
Staff of the ARB estimated diesel exhaust PM concentrations for California's 15 air basins10
(see Figure V-1) using receptor modeling techniques, which include chemical mass balance modelresults from several studies. This method provides a means to apportion sources of primary PM10
on a site-by-site basis, and is used to estimate population-weighted annual averaged outdoorconcentrations statewide. Studies from the San Joaquin Valley (1988-89), South Coast (1986),and San Jose (winters of 1991-1992 and 1992-1993) were used to obtain speciated PM ambient10
data. The ARB staff used these studies along with the ambient PM monitoring network data, and10
the 1990 PM emissions inventory, in a receptor model approach to estimate statewide outdoor10
concentrations of diesel exhaust PM . 10
In each of the studies used to estimate diesel exhaust PM concentrations, researchers used a10
chemical mass balance model to apportion primary sources of PM to diesel exhaust. Using their10
methods and results along with several assumptions, staff of the ARB were able to extract thediesel exhaust PM concentrations from the San Joaquin Valley, South Coast (including the10
Southeast Desert), and San Jose areas.
San Diego
Mojave Desert
South Coast
San JoaquinValley
Great BasinValleys
South CentralCoast
North CentralCoast
San FranciscoBay Area
Lake Tahoe
SacramentoValley
NortheastPlateau
NorthCoast
LakeCounty
MountainCounties
Salton Sea
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Calculations for the other 12 air basins in California were based on the DRI SJV sourceapportionment study results to estimate average fractions for rural and urban exposures (DRI,1990). Air monitoring data for California were extracted from the 1988 through 1992 versions ofthe California Air Quality Data Summary, Air Quality Data Gaseous & Particulate PollutantsReport (CAQDS report), published by the ARB's Technical Support Division. The 1990 PM10
Emission Inventory for diesel exhaust analysis and the CAQDS report were used to extrapolate thePM concentrations from diesel exhaust in the San Joaquin Valley (SJV) to the other 12 air basins. 10
The SJV is used as a surrogate because the chemical mass balance results are the most recent andinclusive of rural and urban areas. By using each basin’s inventory, basin-specific results wereobtained (see Appendix B of this report).
Figure V-1California's 15 Air Basins
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Using an interpolation model and population distribution model, staff calculated thepopulation-weighted annual average diesel exhaust PM concentration for all the air basins using10
1990 census data for California (Appendix B).
With the sources of data outlined above, a number of assumptions were made. Some of theassumptions include: 1) using diesel exhaust PM as a subset of the primary motor vehicle10
category of the chemical mass balance results, 2) the diesel exhaust subset may be determined fromthe motor vehicle emission inventory, and 3) the sampling sites within the SJV can be characterizedas rural or urban and this characterization can be further extrapolated to other air basins wheresource apportionment data are not available (See Appendix B for a detailed discussion of theapproach taken and the assumptions used). The results of our analysis have been extensivelydiscussed at public workshops and have incorporated public comments. We believe our approachused to estimate Californians’ outdoor ambient exposure to diesel exhaust PM reflects the best10
available science and methods.
C. Estimated Concentrations of Outdoor Ambient Diesel Exhaust PM 10
in California
Table V-2 summarizes the ARB staff-estimated ambient concentrations of diesel exhaust PM10
in California. The statewide population-weighted annual outdoor average diesel exhaust PM10
concentration is 3.0 Fg/m . The basin-wide average diesel exhaust PM concentrations range310
from 0.2 Fg/m (Great Basin Valleys Air Basin) to 3.6 Fg/m (South Coast Air Basin). These3 3
concentrations are within the range of estimates given by other researchers (see Table V-1). The statewide population-weighted annual outdoor average diesel exhaust PM10
concentration estimate represents, in general, what most Californians may be exposed to, although14 out of the 15 air basins with less population have values below the statewide average.
The ARB staff have also estimated 1995 outdoor ambient exposure concentrations based onlinear extrapolations from the 1990 to the 1995 emissions inventories using linear rollbacktechniques. Linear rollback techniques are used to estimate the projected ambient concentrationsof primary sources with respect to the base year emissions inventory. For this technique, a one-to-one correspondence between basin-wide emissions and source contributions at a given site isassumed. It is assumed that the changes in a specific source category, due to growth or emissioncontrol, will not greatly alter the distribution of emissions from that source category, and thusaffect the outdoor ambient concentration estimate. Using this technique, we estimated 1995outdoor ambient concentration of diesel exhaust PM in California of 2.2 Fg/m .10
3
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Table V-2Average Ambient Outdoor Concentrations of Diesel Exhaust PM10
in California for 1990
Air Basin Air Basin Population Diesel Exhaust PM 10
(Fg/m ) 3
Great Basin Valleys 29,000 0.2 Lake County 51,000 0.3 Lake Tahoe 21,000 1.0 Mojave Desert 557,000 0.8Mountain Counties 485,000 0.6 North Central Coast 622,000 1.4 North Coast 564,000 1.2 Northeast Plateau 80,000 1.1 Sacramento Valley 2,219,000 2.5 Salton Sea 330,000 2.6San Diego 2,504,000 2.9 San Francisco Bay Area 5,967,000 2.5 San Joaquin Valley 2,658,000 2.6 South Central Coast 1,232,000 1.8South Coast 12,809,000 3.6
D. Diesel Exhaust PM Outdoor Ambient Air Concentration Projections10
As with the 1995 estimated outdoor ambient exposure estimation, linear rollback techniquesare used to project the ambient diesel exhaust PM concentration for the years 2000 and 2010. 10
Figure V-2 shows the estimated and projected PM outdoor ambient concentrations based on the10
emissions inventory from diesel exhaust emissions for the base year, 1990 and 1995, and theprojected years 2000, and 2010. Based on the emissions inventory projections, staff estimates thatoutdoor ambient diesel exhaust PM concentrations decreased from 3.0 Fg/m in 1990 to 10
3
2.2 Fg/m in 1995. By 2000 and 2010, concentrations are projected to be 1.8 Fg/m and 3 3
1.7 Fg/m , respectively.3
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Figure V-2Estimated PM Concentrations10
Attributed to Emissions from Diesel Exhaustfor 1990, 1995, 2000, 2010
E. Near-source Emissions and Exposures
Approximately 60 percent of California's diesel exhaust PM is emitted on roadways by10
heavy-duty trucks, buses, and light-duty passenger vehicles. People living and/or working nearbusy roadways or intersections are exposed to higher-than-average concentrations of dieselexhaust.
The ARB staff conducted a study in 1993 to determine the PM concentrations due to the10
primary emissions from diesel engine exhaust near the Long Beach Freeway. Ambient carbon datawas collected for three days in December 1993 on both sides of the freeway as well as on the roofof a school gymnasium located 1.5 miles away to obtain background concentrations. Themeasured carbon data, elemental and organic, were then used to estimate near-freeway dieselexhaust PM concentrations. In addition, information from other studies on motor vehicle EC/OC10
source profiles, ARB’s emission estimates from its EMFAC7G model, and a system of equationswere used to estimate the concentrations. Results indicate that near-roadway concentrations ofdiesel exhaust PM may be as high as 8 Fg/m above ambient concentrations for one 24-hour10
3
period (ARB, 1996; Appendix C of this report).
This estimate is similar to the result that researchers at Volkswagen (1989) obtained fromdispersion models to estimate typical U.S. roadway exhaust PM concentrations that would resultfrom light-duty vehicle emissions. PM emissions from heavy-duty diesel vehicles were notincluded in the models. The researchers estimated that the vehicle-derived PM concentrations nearan expressway could be as high as 7.1 Fg/m (4 meters from the road), while PM concentrations in3
an urban street canyon could be as high as 8.8 Fg/m (1 meter from the curb). Even without3
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adding the contribution of heavy-duty vehicles, near-road PM concentrations estimated in thisstudy for typical U.S. roadways are about twice the average ambient statewide population-weighted diesel exhaust PM concentration of 3.0 Fg/m .10
3
Diesel exhaust drifting away from stationary sources can significantly increase outdoor dieselexhaust concentrations (and the resulting public risk) in impacted areas. Higher-than-averageexposures to diesel exhaust can occur near powerplants, oil production facilities, pumping stations,construction sites, shipping docks, railroad yards, truck parks, heavy equipment repair facilities,bus terminals, and other point or area emission sources where heavy-duty diesel engine operationis common.
1. Occupational Exposure
Occupational exposure studies have certain advantages over environmental studies conductedin outdoor ambient atmosphere. The diesel exhaust concentrations are generally higher, theexposed workplace population is better defined, duration of exposure more predictable, andsources of diesel exhaust are usually definable.
For example, Froines et al. (1987) reported PM concentrations (primarily diesel exhaust PM)inside urban fire stations from less than 100 Fg/m to as high as 480 Fg/m , depending on the3 3
number of runs during the sampling period (8-hour). Personal sampling was used to measure totalairborne particulate in several fire stations in New York, Boston, and Los Angeles. The authorssought the participation of nonsmokers to reduce the potential for elevated results due to theparticles emitted from tobacco smoke. The fire stations acted as emission sources as the exhaustescaped from the buildings; the researchers reported outdoor PM concentrations ranging from 30to 120 Fg/m . The study also estimated a “worst-case” scenario. In a Los Angeles fire station,3
concentrations as high as 748 Fg/m were found. This represents an upper bound for the3
concentration of particles likely to be found in fire stations.
Recent industrial surveys of miners, forklift truck operators, truck drivers and railroadworkers indicate a wide range of daily occupational exposures to PM in diesel exhaust (4 to 1,700 Fg/m ). Mine workers in enclosed spaces were exposed to the highest concentrations.3
NIOSH estimates that approximately 1.35 million people are exposed to diesel exhaust in theworkplace. The 8-hour average measured concentrations of diesel particulate range from 100 to1,000 Fg/m and levels in excess of 2,000 Fg/m have been reported (NIOSH, 1988).3 3
In another study, and as part of a case control mortality study of trucking industry workers,exposures to diesel aerosol, via elemental carbon, were measured among four exposed job groups(road drivers, local drivers, dockworkers, and mechanics). In this study, eight industrial hygienesurveys were conducted at eight U.S. terminals and truck repair shops. A single-stage personalimpactor was used to collect submicrometer-sized diesel particulates. All of the samples weretaken over a full shift (approximately 8 hours) to maximize sensitivity. Results from these surveysindicated that overall average exposures to EC ranged from 5.1 Fg/m in road (long distance)3
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drivers to 26.6 Fg/m in mechanics. These were significantly higher than average background3
concentrations, measured at the same locations where workers were sampled, of 3.4 Fg/m on3
major highways and 1.4 Fg/m in residential areas (Zaebst, et al. 1991). By assuming that the3
percentage of diesel exhaust-derived EC in Los Angeles (approximately 67 percent) and that diesel exhaust particles are about 64 percent EC (Gray et al., 1986) applies toother urban areas, we calculated approximate concentrations of diesel exhaust PM to range from5.3 to 27.8 Fg/m . 3
As part of the epidemiology studies used to estimate exposures to railroad workers,measurements were made to characterize workers’ exposure to diesel exhaust. Personal samplesto respirable particulate matter for over 530 workers in 39 jobs in four U.S. railroads over a three-year period were made. The samples were adjusted to remove the fraction of cigarette smoke, orcalled the adjustable respirable particulate (ARP). The geometric mean exposures to the ARPranged from 17 Fg/m for clerks to 134 Fg/m for locomotive shop workers 3 3
(Woskie et al., 1988).
F. Indoor and Total Air Exposure
People spend a majority of their time indoors. To accurately estimate the population’sexposure to toxic air pollutants, risk assessors must consider both the amount of time people spendin different environments and the concentrations of the pollutants of interest in those environments.
To estimate Californians’ exposures to diesel exhaust particles, ARB staff used estimates ofpopulation-weighted ambient diesel exhaust particle concentrations (discussed in sections B and Cof this Chapter and in detail in Appendix B) in a model that can estimate indoor air concentrations,population indoor air exposure, and total air exposure. The model, called the CaliforniaPopulation Indoor Exposure Model (CPIEM), was recently developed under contract to the ARBto improve estimates of population exposures to toxic air pollutants (Koontz et al., 1995). Themodel generally uses distributions of data (rather than single values) as inputs, and a Monte Carlo(repeated random sampling) simulation approach. ARB’s model estimates developed usingCPIEM are summarized here and discussed in more detail in Appendix D.
Because representative data on indoor concentrations of diesel exhaust particles are notavailable, population-weighted outdoor concentrations of diesel exhaust particles plus other inputs(such as distributions of California building air exchange rates) were used in a mass-balance model(provided as one of two modules in CPIEM) to estimate indoor air concentrations of dieselexhaust particles for different indoor environments. Using these indoor air concentrationdistribution estimates, the second module of CPIEM that combines adults and children’s activitypattern data and air concentration data was used to estimate Californians’ exposures to dieselexhaust particles across all enclosed environments. In addition, CPIEM was used to provideestimates of the population’s total air exposure to diesel exhaust particles by combining indoor andoutdoor air exposure estimates.
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In estimating indoor air concentrations for different indoor environments, input data andvarious assumed values for six parameters were entered into the mass balance model. The sixparameters were: the outdoor concentration distributions of diesel exhaust particles; air exchangerates; penetration factor; volume of the indoor space; indoor source emissions rate (set to zero);and a net loss factor that accounts for removal of particles from the indoor space. The statewidepopulation-weighted annual average outdoor diesel exhaust particle concentration estimate of 3.0+ 1.1 Fg/m (standard deviation) was used as the outdoor concentration input distribution. The3
mass-balance module was used to estimate indoor diesel exhaust particle concentrations for thefour indoor environments (residences, office buildings, schools, and stores/retail buildings) inCPIEM for which specific data for one or more of the input parameters are available. Estimatedindoor concentrations for these environments are shown in Table V-3 and range from 1.6 + 0.7 Fg/m to 2.1 + 0.9 Fg/m . These and other estimates developed using CPIEM are3 3
discussed further in Appendix D.
No data for input parameters were found for the other enclosed environments used in theexposure module of CPIEM; consequently, those environments were assigned surrogate dieselexhaust particle distributions equal to the distributions estimated for similar types of buildings orenvironments. As shown in Table V-3, industrial plants and enclosed vehicles were assigned thepopulation-weighted average outdoor concentration values, restaurants and lounges were assumedto have levels similar to those found in stores and retail buildings, and “other indoor places” wereassumed to have levels similar to those in office buildings.
The distributions of indoor concentration estimates shown in Table V-3 were used as inputs inthe exposure module of CPIEM, which combines concentration data and data on Californians’activity patterns to develop time-weighted population exposure estimates. The results, shown inTable V-4, indicate that Californians were are exposed to average diesel exhaust particle concentrations of 2.0 + 0.7 Fg/m in indoor environments in 1990. The population time-weighted3
average total air exposure concentration across all environments (including outdoor) is 2.1 + 0.8 Fg/m . This is about two-thirds of the population-weighted ambient average3
concentration. The integrated exposure estimates in Table V-4 predict the average exposure todiesel exhaust particles experienced by Californians indoors and across all environments. Both theintegrated exposure estimates and the average air exposure concentration estimates take intoaccount the differences in air concentrations in different environments and the time spent byCalifornians in those environments.
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Table V-3Estimated Statewide Air Concentrations of Diesel Exhaust Particles
used as Exposure Module Inputs (FFg/m )*3
Estimated Mean Surrogate MeanEnvironment (+ std dev) (+ std dev)
Similar indoor concentration and exposure calculations were conducted for the South CoastAir Basin and the San Francisco Bay Area. For the South Coast, the population-weighted outdoorconcentration input distribution was 3.6 + 1.4 Fg/m ; the resulting estimated population average3
indoor exposure concentration was 2.4 + 0.9 Fg/m , and the population average total exposure3
concentration was 2.5 + 0.9 Fg/m . The input population-weighted outdoor concentration3
distribution use for the San Francisco Bay Area was 2.5 + 1.6 Fg/m ; the resulting estimated3
population average indoor exposure concentration was 1.7 + 0.9 Fg/m , and the population3
average total exposure concentration was 1.7 + 0.9 Fg/m .3
Table V-4Estimated Exposure of Californians to Diesel Exhaust Particles for 1990
Time in Integrated Average AirEnvironment Daily Exposure Exposure Conc.(Mean hours) (Fg-hr/m ) (Fg/m )* 3 3
Total Indoor(Enclosed) Exposure 22.5 48 + 18 2.0 + 0.7
Total Air Exposure 24 53 + 18 2.1 + 0.8______________________________________________________________________________* Values significant to one digit (whole numbers); calculated values shown here are rounded to
two digits for informational purposes.
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It is important to note that these estimates are population estimates based on very limited inputdata and a number of assumptions. These estimates are “improved” over previous estimatesbecause they incorporate into the exposure calculation both Californians’ activity patterns and thereduced air concentrations of diesel exhaust particles in indoor environments relative to levelsmeasured at ambient monitoring stations. However, they include notable uncertainty and do notadequately reflect the great variability of exposures that Californians are likely to experience overtime. Of particular concern is the fact that higher exposures (the upper tail of the distribution) arelikely to be underestimated and are not fully identified in this type of analysis, largely because theprimary input (the annual average outdoor concentration calculated from ambient station data)does not necessarily reflect elevated diesel exhaust particle levels in “hot spot” locations and dataare not available for environments such as inside vehicles where levels typically would be elevated. Individuals whose occupation or leisure activities keep them in close proximity to diesel exhaustfor extended periods would be exposed to much higher levels of diesel exhaust particles than arereflected by the average estimated levels (and the distributions) shown in Tables V-3 and V-4.
1. Indoor and Total Air Exposure Estimates for 1995, 2000, and 2010
The estimated average indoor air exposure concentration associated with the 1995, 2000, and2010 estimated outdoor average population-weighted exposure concentrations of 2.2 Fg/m , 3
1.8 Fg/m , and 1.7Fg/m , respectively, is estimated to be approximately 1.47 Fg/m for 1995, 3 3 3
1.2 Fg/m for 2000, and 1.13 Fg/m for 2010. The average total air exposure concentration for3 3
the years 1995, 2000, and 2010 is estimated to be about 1.54 Fg/m , 1.26 Fg/m , and 1.19 Fg/m ,3 3 3
respectively (see Table V-5). The discussion below demonstrates how these estimates were madeusing the method for calculating 1995 estimates as an example.
These estimates were not developed by using the CPIEM model as were the earlier estimatesfor the 1990 baseline year. Because of the uncertainties associated with the outdoor ambientpopulation-weighted average exposure concentrations for 1995, 2000, and 2010, and the lack ofdistributional information (such as a standard deviation) for these estimates, it is not appropriate touse the CPIEM to develop detailed indoor and total air exposure concentration estimates. Instead,to provide parallel average indoor and total air exposure estimates for 1995, 2000, and 2010, theratios of the 1990 average indoor and total air exposure estimates to the 1990 population-weightedaverage outdoor concentration estimate were calculated and applied to the corresponding 1995,2000, and 2010 outdoor estimates. The ratio of the 1990 estimated average indoor air exposureconcentration to the 1990 population-weighted outdoor average concentration is 2.0/3.0. Usingthis ratio, we calculated the time-weighted average indoor exposure concentrations for 1995,2000, and 2010. Two-thirds of 2.2 Fg/m (the 1995 outdoor population-weighted average3
1.47 Fg/m , 1.2 Fg/m and 1.13 Fg/m , respectively. The ratio of the 1990 baseline total air3 3 3
exposure to the population-weighted outdoor average concentration is 2.1/3.0. Taking 2.1/3 times the corresponding population-weighted outdoor levels for 1995, 2000, and 2010, weestimate average total air exposure concentrations to be 1.54 Fg/m for 1995, 1.26 Fg/m for3 3
2000, and 1.19 Fg/m for 2010. These calculations assume that the ratios of the indoor and total3
air exposure concentrations relative to the estimated population-weighted ambient levels do not
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change over time, which may or may not be true due to changes in activity patterns and otherfactors. These estimates are approximations only, and are provided to allow some comparison tothe 1990 baseline estimates.
These total exposure estimates are believed to underestimate, to an unknown extent,Californians’ actual exposures to diesel exhaust particles. This is because insufficient data areavailable for concentrations inside vehicles and along roadways to allow such near-source, elevatedexposures to be estimated for the population. Instead, in estimating total exposure, in-vehicle androadway concentrations were assumed to equal the ambient outdoor population-weightedconcentration. The few roadside data available indicate that in-vehicle and roadside levels wouldtypically be several times higher than those measured at nearby ambient stations. Thus, becauseadult Californians spend an average of seven percent of their time inside vehicles, and at least onepercent of their time walking or biking along roadways, elevated concentrations in thoseenvironments would increase the population’s total exposure.
Table V-5Estimated Exposure of Californians to Diesel Exhaust Particles for 1995, 2000, 2010
Estimated Average 1990 Estimated Average Air ExposureAir Exposure Ratio Concentration
Concentration - 1990 FFg/mFFg/m (std. dev.)3
3
1995 2000 2010
AmbientEstimate
3.0 (1.1) 2.2 1.8 1.7
Total IndoorExposureEstimate
2.0 (0.7) 2.0/3.0 2/3 x 2.2 2/3 x 1.8 2/3 x 1.7 = 1.47* = 1.20* = 1.13*
Total AirExposureEstimate
2.1 (0.8) 2.1/3.0 2.1/3 x 2.2 2.1/3 x 1.8 2.1/3 x 1.7= 1.54* = 1.26* = 1.19*
* Significant to two figures
G. Relevant Indoor Air Quality Studies
Data from a variety of studies were reviewed by ARB staff to develop the inputs to CPIEMto estimate diesel exhaust particle concentrations in indoor environments for use in exposuremodeling. Except for indoor elemental carbon data collected for one study of southern Californiamuseums, there are no data available that can be used to directly estimate diesel exhaust particleconcentrations inside enclosed environments. However, there is a small but increasing number ofstudies on building air exchange rates, particle penetration factors, indoor particle deposition and
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sink effects, and other factors that can be used, in combination with outdoor diesel exhaustparticle concentration estimates, to estimate concentrations of diesel exhaust particles in indoorenvironments. Some of those studies were conducted in California and provide California-specificdata. The major studies used in the modeling work described in the previous section arediscussed briefly below. All of the studies reviewed for the modeling work and the specific datafrom those studies used to develop the model inputs are discussed in Appendix D of this report.
1. Residential Studies
The Particle Total Exposure Assessment Methodology (PTEAM) Study provided importantinput data for residential air exchange rates, particle outdoor-to-indoor penetration factors, andindoor particle removal rates for modeling residential concentrations of diesel particles. In thePTEAM study, investigators measured PM and PM metals, and other pollutants in 10 2.5,
178 homes in southern California in the summer and fall of 1990 (Clayton et al., 1993). The airexchange rates (number of air changes of the volume of air in the house with outdoor air perhour) measured in those homes averaged 1.25 with a standard deviation of 1.02, and thus covereda broad range of air exchange situations that would be expected (Ozkaynak et al., 1994). Thepenetration factor calculated by the investigators for PM was estimated to equal one, meaning2.5
that essentially all of the fine particles present in the outdoor air that entered the homes made itpast the building shell. The indoor particle removal rate (due to indoor deposition and sinkeffects) was estimated to be about 0.4 per hour.
These PTEAM estimates were relied upon more heavily than estimates from other studies inmodeling residential indoor concentrations of diesel exhaust particles for several reasons. ThePTEAM data were collected from California homes, they are fairly recent, and they are based on areasonable sample size. Most important, the investigators examined the relationships among airexchange rate, penetration factor, and indoor removal rate and provided estimates for all of thesevariables. Because these factors are inter-related, a data set such as that provided by PTEAM issomewhat more reliable for modeling purposes than data sets that provide information on onlyone of these factors.
In addition to the PTEAM study, a number of other California studies have includedmeasurements of air exchange rates in homes in various regions of the state and during differentseasons. Together, they provide a useful body of data for estimating annual air exchange rates forCalifornia homes. Air exchange rate measurements obtained during winter or from newer, moreair-tight, California homes were available for over 1000 California homes; the average ratesranged from about 0.5 to 0.9 (Sheldon et al., 1993; BSG, 1990; Wilson et al., 1993; Wilson et al.,1986; Pellizzari et al., 1989). The average air exchange rates measured in a total of about 500California homes during the summer ranged from about 0.7 to 2.8 (BSG, 1990; Wilson et al.,1986; ADM, 1990; Pellizarri et al., 1989). Data for fall and spring values, which fall somewherein between the summer and winter values, were available from more than 700 California homes(BSG, 1990; Wilson et al., 1993; Wilson et al., 1986). The use of the data from these studies to develop a distribution of air exchange rates is described in Appendix D.
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Penetration factor estimates for residences were based on a review of studies that providemodeled penetration factors based on various measured values. In the major California studydiscussed above, PTEAM investigators estimated a penetration factor of one for PM and nearly2.5
one for PM (Ozkaynak et al., 1994). Other field study investigators have estimated penetration10
factors of less than one in residences. In a large field study of 394 homes, Koutrakis et al., (1992)estimated a penetration factor of about 0.84 for particles smaller than 2.5 microns. Results fromsmaller studies of 68 and 47 homes indicated penetration factors of 0.7 to 0.85 (Suh et al., 1994;Dockery and Spengler, 1981). In a winter study of 10 homes in Boise, Idaho conducted for theU.S. EPA's Integrated Air Cancer Project, investigators estimated an infiltration factor of about0.5 for fine particles and 1.0 for VOCs, based on indoor/outdoor ratios of pollutants in homeswith very low air exchange rates (0.2 - 0.8).
In a single, two-story California home, Thatcher and Layton (1995) investigated in detail therelationships among penetration, deposition, resuspension, and airborne particle concentrationsindoors. The deposition velocities for particles were measured by raising the particleconcentration indoors and simultaneously measuring air infiltration rates and particleconcentration decay rates. Based on sampling results on different days, the indoor deposition ratefor particles from 1 to 3 µm in diameter ranged from about 0.25 to 0.75 per hour, and depositionrates for particles 3 to 10 µm in diameter ranged from about 0.75 to 1.78 per hour. Theinvestigators estimated the penetration factor for both particle fractions based on theexperimentally determined deposition velocities and indoor/outdoor particle concentration ratios. For both particle fractions, the penetration factor was calculated to be nearly one; theinvestigators indicated that this shows that the building shell is not effective at removing particlesas air enters the building. These test home results are consistent with the field study estimatesobtained by Ozkaynak et al. (1994). Because Thatcher and Layton and Ozkaynak et al. bothaccounted for indoor deposition in their calculation of penetration factor, results from thesestudies were weighed more heavily in developing estimates of penetration factor and net indoorremoval for the model, as discussed in Appendix D to this report.
2. Studies of Commercial and Public Buildings
Air exchange rate data for commercial and public buildings are provided by three studies,only one of which is a California study. Grot (1995) measured air exchange rates in 49 non-residential buildings located throughout the State of California. These buildings included 14 schools, 22 office buildings and 13 retail buildings. The measurements were taken for thebuildings when their air handling systems were purposely set at minimum damper settings. Therefore, the data represent the natural infiltration rates of the buildings with a minimuminfluence from the air handling systems, and thus provide conservative (low) estimates of thetypical in-use air exchange rates. The school buildings had the highest mean air exchange rate at2.45 air changes per hour. The mean rate for retail buildings was 2.22, and the mean rate foroffice buildings was 1.35. For both office and retail buildings, large buildings were shown to havelower air exchange rates than small buildings.
In a second study, the National Institute of Standards and Technology conducted over
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3000 measurements of air exchange rates in 14 U.S. office buildings (Persily, 1989). Theseincluded 2- to 15-story buildings which were mechanically ventilated by different types of heating,ventilating, and air conditioning (HVAC) systems. Investigators monitored each building forabout a year under a range of weather and building operation conditions. The mean air exchangerate of all the measurements was 0.94 air changes per hour. The mean air exchange rate ofindividual buildings ranged from 0.29 to 1.73 (medians ranged from 0.25 to 1.65). In a thirdstudy, Turk et al. (1987) obtained air exchange measurements ranging from 0.3 to 4.1 in 38 buildings in the Pacific Northwest. The mean air exchange rate was 1.5.
Penetration factor data were not available for common public and commercial buildings. Because many public and commercial buildings have central HVAC systems that actively bring inoutdoor air and filter the outdoor air, re-circulated indoor air, or both, distributions of penetrationfactors were estimated for different types of buildings. A single study provided information onthe percent of different types of buildings that have active air filtration. BSG (1993) conducted atelephone survey to gather information about HVAC systems of non-residential buildings inCalifornia. Participants were specifically asked whether a filtration system was used in their airhandling units. Complete information was provided on 88 buildings. These included 26 officebuildings, 28 retail buildings and 34 schools. About 76% of school buildings, 64% of retailbuildings and 73% of office buildings in the survey had filtered air. Approximately 20% of thebuildings surveyed had only unfiltered air.
Data from several studies on filter efficiencies and the fraction of air filtered (Sinclair et al.,1990 and 1992; Weschler et al., 1983 and 1995; Ligocki et al., 1993) were used in combinationwith the BSG (1993) data to estimate distributions of penetration factors for different types ofbuildings. These data are very limited, but cover a range of building types including museums,telecommunications buildings, and manufacturing plants. The use of these studies to estimateparticle penetration for public and commercial buildings is described in Appendix D and in TablesC4 and C5 of Appendix D.
In one of these studies, the investigators examined elemental carbon levels indoors inmuseums. Their results showed that indoor concentrations of elemental carbon vary with the airexchange rate and with the type of HVAC system used and the extent of particle filtration. Ligocki, et al. (1993) measured elemental carbon concentrations in and around five museums inSouthern California during the summer of 1987 and the winter of 1987-1988. The five museumswere the Getty Museum in Malibu, the Norton Simon Museum in Pasadena, the Scott Gallery inSan Marino, the Southwest Museum in Los Angeles, and the Sepulveda House in downtown LosAngeles. The first three museums are modern buildings with custom heating, ventilation, and airconditioning (HVAC) systems with particle filtration. The Southwest Museum has a HVACsystem in the hall, but no particle filtration system. The Sepulveda House is a historical museumwith no HVAC system--when the weather is warm it is often operated with the doors andwindows open. Seasonal averages for elemental carbon in the museums ranged fromapproximately 0.14 Fg/m at the Getty Museum during the summer, to 7.4 Fg/m at the3 3
Sepulveda House during the winter. The ratios of indoor to outdoor air concentrations of fineparticles ranged from approximately 1:5 at the Norton Simon Museum (with the best HVAC
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system) to approximately 1:1 at the Sepulveda House (Nazaroff et al., 1990; Ligocki, et al.,1993).
As reported earlier in this Chapter (see 3.b. Elemental Carbon Source Apportionment), Gray(1986) determined that diesel exhaust contributes 67 percent of the Los Angeles area's airborneEC, and that an average diesel exhaust particle is about 64 percent EC. If this is the case, then theindoor diesel exhaust PM concentrations in the museums may have ranged from approximately0.15 Fg/m (in the buildings with modern HVAC systems) to 7.7 Fg/m (in the Sepulveda House3 3
with no HVAC). Corresponding outdoor diesel exhaust particulate matter concentrations mayhave ranged from approximately 0.03 to 7.7 Fg/m .3
H. Other Routes of Diesel Exhaust Exposure (Multipathway)
Exposure assessment also involves determining concentrations of the various pollutants inmedia by which humans are exposed. Air emissions contaminate not only the air, but deposit ontowater, soil, and vegetation. These media represent the additional possible pathways of exposure toambient diesel exhaust concentrations. In order to estimate long-term exposures resulting fromambient concentrations, the risk assessment must address both inhalation and non-inhalationpathways of exposure.
Multiple exposure pathways may contribute to the total exposure to a pollutant. Forhumans, the primary pollutant exposure pathways are inhalation, ingestion of dirt andcontaminated food products, water ingestion, and dermal absorption of pollutants orcontaminated dirt deposited on the skin. The secondary pathways are a result of the assimilationof the pollutant into a food source.
In order to assess non-inhalation pathways, substance and site-specific data are needed. Since the specific parameters for diesel exhaust are not known for these pathways, a multi-pathway assessment for diesel exhaust exposure was not done. More research is needed in thisarea for diesel exhaust.
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J. References for Chapter V
ADM (1990), "Pilot Residential Air Exchange Survey, Task 2: Pilot Infiltration Study, IndoorAir Quality Assessment Project," Report to the California Energy Commission prepared byADM Associates, Inc., Sacramento, CA, Contract No. 400-88-020.
ARB, 1996. Evaluation of Carbon Samples Collected Near a Freeway to Determine the AboveAmbient Levels of PM due to Diesel Emissions from Diesel Engine Exhaust. Report10
requested from the Stationary Source Division, prepared by the Technical Support Division.19 July 1996.
BSG (1990), "Occupancy Patterns and Energy Consumption in New California Houses (1984-1988)," California Energy Commission Consultant Report (P400-90-009), prepared by Berkeley Solar Group and Xenergy, Oakland, CA.
BSG (1993) "Outdoor Air Exchange Rates in Nonresidential Buildings, Task 2: Survey Instrument Selected Sample Pilot Study," Report to the California Energy Commission prepared by the Berkeley Solar Group, Oakland, CA, Contract No. 400-90-028.
Chow J.C., Watson J.G., Richards L.W., Haase D.L., McDade C., Dietrich D.L., Moon D. and C. Sloane, 1991. “The 1989-90 Phoenix PM Study. Volume II: Source10
Apportionment. Final Report.” DRI Document No. 8931.6F1, prepared for ArizonaDepartment of Environmental Air Quality, Phoenix, AZ, by Desert Research Institute, Reno,NV.
Clayton, C.A., R.L. Perritt, E.D. Pellizzari, K.W. Thomas, R.W. Whitmore, L.A.Wallace, H. Ozkaynak, and J.D. Spengler, (1993), "Particle Total Exposure Assessment Methodology(PTEAM) Study: Distributions of Aerosol and Elemental Concentrations in Personal, Indoor,and Outdoor Air Samples in a Southern California Community,” Journal of ExposureAnalysis and Environmental Epidemiology 3(2): 227-250.
Cuddihy R.G., Griffith W.C., Clark C.R. and R.O. McClellan, 1981. Potential Health and Environmental Effects of Light Duty Diesel Vehicles II, Inhalation Toxicology Research Institute, Lovelace Biomedical and Environmental Research Institute, prepared for the U.S. Department of Energy, LMF-89, UC-48, October.
Denton J.E., Hughes K.V., Ranzieri A.J., Servin A., Dawson S.V., Alexeeff G.V., Smith A.H., Bates M.N. and H.M. Goeden, 1992. Development of Exposure and Toxicity Data forDiesel Exhaust in California. ARB Technical report ARB/SS-92-01, October.
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References for Chapter V (continued)
Desert Research Institute, 1990. San Joaquin Valley Air Quality Study Phase 2: PM-10 Modeling and Analysis, Volume I: Receptor Modeling Source Apportionment, DRI
Document No. 8929.1F, October 11.
Dockery, D.W. and J.D. Spengler (1981), "Indoor-Outdoor Relationships of Respirable Sulfates and Particles," Atmospheric Environment 15: 335-343.
Froines J.R., Hinds W.C., Duffy R.M., Lafuente E.J. and W.C.V. Liu, 1987. Exposure of Firefighters to Diesel Emissions in Fire Stations. Am. Ind. Hyg. Assoc. J., 48 (3), 202-207.
Gray H.A., 1986. Control of Atmospheric Fine Primary Carbon Particle Concentrations. EQL Report No. 23, Environmental Quality Laboratory, California Institute of Technology, Pasadena, CA.
Gray H.A., Landry B., Liu C.S., Henry R.C., Cooper J.A., and J.R. Sherman, 1989. Receptor Modeling for PM Source Apportionment in the South Coast Air Basin of 10
California. Air Quality Management Plan, 1989 Revision, Appendix V-K. South Coast AirQuality Management District.
Grot, R.A. (1995) "Air Change Rates in Non-residential Buildings in California," California Energy Commission Consultant Report P400-91-034BCN.
Horvath H., Kreiner I., Norek C. and O. Preining, 1988. Diesel Emissions in Vienna. Atmos. Environ., 22(7), 1255-1269.
Hsieh D.P.H., Kado N.Y., Okamoto R., Kuzmicky P., Rathbun C. and J. Ito, 1993. Measurement and Chemical Characterization of Vapor-Phase Mutagens in Diesel Exhaust. Final Report Prepared for the California Air Resources Board, Contract No. A032-095.
Ingalls M.N., 1985. Improved Mobile Source Exposure Estimation, Southwest Research Institute, EPA-460/3-85-002, March 1985.
Koontz M.D., W.C. Evans and C.R. Wilkes, 1995. Development of a Model for Assessing Indoor Exposure to Air Pollutants. Draft Final Report to the California Air ResourcesBoard, Contract No. A933-157.
Koutrakis, P., S.L.K. Briggs and B.P. Leaderer (1992), "Source Apportionment of Indoor Aerosols in Suffolk and Onondaga Counties, New York," Environ. Sci. Technol. 26:521-527.
References for Chapter V (continued)
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Krieger R.K., Denton J.E., Dawson S.V. and G.V. Alexeeff, 1994. Presented at theProceedings of the 5th Annual West Coast Regional Conference of the Air & WasteManagement Association Meeting, November 9-10, 1994. Publication “Current Issues in AirToxics.”
Ligocki M.P., Salmon L.G., Fall T., Jones M.C., Nazaroff W.W. and G.R. Cass, 1993. Characteristics of Airborne Particles Inside Southern California Museums. Atmos. Environ., 27A(5), 697-711.
McClellan R.O., 1986. Health Effects of Diesel Exhaust: A Case Study in Risk Assessment, Am. Ind. Hyg. Assoc. J., 47(1):1-13, 154.
National Institute for Occupational Safety and Health (NIOSH), 1988. Current Intelligence Bulletin No. 50: Carcinogenic Effects of Exposure to Diesel Exhaust. Publication No. 88-116. NIOSH, Cincinnati, Ohio.
Nazaroff W., Salmon L. and G.R. Cass, 1990. Concentration and Fate of Airborne Particles in Museums. Environ. Sci. Technol., 24(1), 66-76.
Ozkaynak, H., J. Xue, R. Weker, D. Butler, P. Koutrakis and J. Spengler (1994), "The ParticleTEAM (PTEAM) Study: Analysis of the Data," May 1994 report to the U.S. EPA., VolumeIII of Final Report.
Pellizzari, E.D., L.C. Michael, K. Perritt, D.J. Smith, T.D. Hartwell and J. Sebestik (1989), "Development and Implementation of Exposure Assessment Procedures for Toxic AirPollutants in Several Los Angeles County, California Communities," Final Report to theCalifornia Air Resources Board, Contract No. A5-174-33.
Persily, A (1989), "Ventilation Rates in Office Buildings," in The Human Equation: Health and Comfort, Proceedings of the ASHRAE/SOEH Conference, IAQ 89. April 17-20, 1989, San Diego, CA pp. 128-136.
Schuetzle D., 1983. Sampling of Vehicle Emissions for Chemical Analysis and Biological Testing. Environ. Health Perspect., 47, 65-80.
Sheldon, L., A. Clayton, J. Keever, R. Perritt and D. Whitaker (1993), "Indoor Concentrations of Polycyclic Aromatic Hydrocarbons in California Residences," Draft FinalReport to the Air Resources Board, Contract No. A033-132.
References for Chapter V (continued)
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Sinclair, J.D., L.A. Psota-Kelty, C.J. Weschler and H.C. Shields (1990), "Measurements and Modeling of Airborne Concentrations and Indoor Surface Accumulation Rates of Ionic Substances at Neenah, Wisconsin," Atmospheric Environment 24A(3): 627-638.
Sinclair, J.D., L.A. Psota-Kelty and G.A. Peins (1992), "Indoor/Outdoor Relationships of Airborne Ionic Substances: Comparison of Electronic Equipment Room and Factory Environments," Atmospheric Environment 26A(5), pp. 871-882.
Suh, H.H., P. Koutrakis and J.D. Spengler (1994), "The Relationship between Airborne Acidityand Ammonia in Indoor Environments," Journal of Exposure Analysis and EnvironmentalEpidemiology 4(1): 1-22.
Thatcher, T.L. and D.W. Layton (1995) "Deposition, Resuspension, and Penetration of Particles within a Residence," Atmospheric Environment, 29(13): 1487-1497.
Turk, B.H., J.T. Brown, K. Geisling-Sobotka, D.A. Froehlich, D.T. Grimsrud, J. Harrison, J.F. Koonce, R.J. Prill and K.L. Revzan (1987), "Indoor Air Quality and VentilationMeasurements in 38 Pacific Northwest Commercial Buildings," Volume 1, LBL-22315 ½, Lawrence Berkeley Laboratory.
U.S. Environmental Protection Agency (EPA), 1983. Diesel Particulate Study, Office of MobileSources, Office of Air and Radiation, October.
Volkswagen, 1989. Unregulated Motor Vehicle Exhaust Gas Components. Volkswagen AG, Research and Development (Physico-Chemical Metrology). Project Coordinator: Dr. K.-H. Lies. 3180 Wolfsburg 1, F.R. Germany.
Weschler, C.J., S.P. Kelty and J.E. Lingousky (1983), "The Effect of Building Fan Operation on Indoor-Outdoor Dust Relationships," Journal of the Air Pollution Control Association 33:624-629
Weschler, C.J., H.C. Shields and B. Shah (1995), "Understanding and Controlling the Indoor Concentration of Sub-Micron Particles at a Commercial Building in Southern California,"Presented at the 88th Annual Meeting of Air and Waste Management Association, June 18-23, 1995, Paper No. 95-MP4.01.
Wilson, A.L., S.D. Colome and Y. Tian (1993) "California Residential Indoor Air Quality Study, Volume 1: Methodology and Descriptive Statistics," Prepared for Gas Research Institute, Pacific Gas and Electric Company and Southern California Gas Company by Integrated Environmental Services, Irvine, CA.
References for Chapter V (continued)
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Wilson A.L., S.D. Colome, P.E. Baker and E.W. Becker (1986), "Residential Indoor Air QualityCharacterization Study of Nitrogen Dioxide," Phase I Final Report for Southern California GasCompany.
Woskie, S.R., Smith, T.J., Hammond, S.K., Schenker, M.B., Garshick, E. And F.E. Speizer. 1988. Estimation of the Diesel Exhaust Exposures of Railroad Workers: I. CurrentExposures. Am. J. Ind. Med., 13, 381-394.
Zaebst D.D., Clapp D.E., Blake L.M., Marlow D.A., Steenland K., Hornung R.W., Scheutzle D. and J. Butler, 1991. Quantitative Determination of Trucking Industry Workers Exposures to Diesel Exhaust Particles. Am. Ind. Hyg. Assoc. J., 52(12), 529-541.
Zielinska B., 1991. Diesel Emissions: New Technology, Health Effects and Emission Control Programs. Final Report. DRI Document No. 8201.FR, Prepared for the Arizona Department of Environmental Quality. Desert Research Institute, Reno, Nevada.
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VI.ATMOSPHERIC PERSISTENCE AND FATE OF DIESEL EXHAUST
Diesel exhaust contains thousands of gas, particle, and particle- associated constituents,including carbon dioxide, carbon monoxide, water vapor, oxides of nitrogen, saturated andunsaturated aldehydes and ketones, alkanes, alkenes, monocyclic aromatic hydrocarbons,carbon-core particles, gas- and particle-phase polycyclic aromatic hydrocarbons (PAH) andPAH-derivatives, and metals (see Chapter III). This wide range of substances has an even widerrange of atmospheric fates. For example, diesel exhaust contains the atmospherically-reactiveanimal carcinogen benzo[a]pyrene (BaP). Van Cauwenberghe et al. (1979) tentatively identified atleast nine BaP derivatives after reaction with tropospheric ozone. Many of these derivatives aredirect-acting mutagens (Finlayson-Pitts and Pitts, 1986).
Diesel exhaust's constituents can react with atmospheric radicals to form new species,combine with other substances to form more complex species, and/or be deposited onto surfaces. In this chapter, we provide a general discussion of what is known about the atmospheric lifetimesand fates of diesel exhaust's major component groups: particles, particle-associated organiccompounds, gas and particle-associated PAH and PAH-derivatives, and gaseous species.
Diesel exhaust contributes to global warming because it contains substances such as methaneand carbon dioxide. Diesel exhaust also contributes to acid deposition because it contains nitricand sulfuric acids, as well as other substances which can be transformed to acidic PM in theatmosphere. Diesel exhaust is not known to contribute to stratospheric ozone depletion.
A. Atmospheric Fate of Diesel Exhaust Particles
The two most important processes affecting diesel exhaust particles in the atmosphere are:
L dry and wet deposition (physical removal) of the particles, andL atmospheric transformations of species adsorbed to the particles.
1. Physical RemovalPhysical removal of diesel exhaust PM from the atmosphere is usually accomplished through
accretion of the particles, atmospheric fall-out (dry deposition), and atmospheric removal by rain(wet deposition).
A particle's atmospheric lifetime due to dry deposition is a function of the particle's diameter(Graedel and Weschler, 1981). Diesel exhaust particles, generally smaller than 1 Fm (Pierson etal., 1983), are expected to remain in the atmosphere from 5 to 15 days.
Rain events result in almost complete wash-out of particles 0.1 to 10 Fm in diameter fromthe atmosphere (Leuenberger et al., 1985; Ligocki et al., 1985a,b). Since diesel exhaust particles
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are in this size range, they are expected to be efficiently washed from the atmosphere when itrains.
2. Atmospheric Reactions of Particle-Associated Organic Compounds Organic compounds absorbed by the particles in the exhaust stream may be protected from
photolysis and/or chemical reaction. Organic species coating the surface of the particles may beexpected to primarily react with sunlight (through photolysis), ozone (O ), gaseous nitric acid3
(HNO ), and nitrogen dioxide (NO ). Organic compounds coating the surface of the particles can2 2
also volatilize from the particle and become more susceptible to photolysis and/or chemicalreaction.
B. Atmospheric Transformations of PAH and PAH-derivatives
This section describes the reactions to PAH in general, keeping in mind that PAH are aproduct of incomplete combustion from a number of sources. Both gas- and particle-phase PAHare found in the atmosphere. Naphthalene and other 2-ring PAH are present in the gas phase inambient air, while the 5- or more-ring PAH (such as the 5-ring benzo[a]pyrene) areparticle-associated (Coutant et al., 1988; Arey et al., 1987, 1989a; Atkinson et al., 1988). Asimilar distribution between gas and particle phase occurs for the PAH-derivatives, with, forexample, nitro-PAH with 4- or more-rings being particle-associated.
In contrast to the PAH (with no atmospheric formation pathways), PAH-derivatives can beformed in the atmosphere from the gas- and adsorbed-phase reactions of the parent PAH. Someof the PAH-derivatives studied in the laboratory have been found to be highly mutagenic (Arey etal., 1986; Atkinson et al., 1990; Atkinson and Arey, 1994).
PAH adsorbed to particles can be transformed into PAH-derivatives by a number ofatmospheric reaction processes, including photolysis and reaction with O , NO and/or HNO ,3 2 3
sulphur dioxide (SO ), and dinitrogen pentoxide (N O ) (Pitts et al., 1978, 1980). For example,2 2 5
particle-associated PAH may photolyze in ambient atmospheres. The extent to which this occursdepends on the properties of the absorbent. Researchers investigating photooxidation andphotolysis of PAH on various surfaces (Korfmacher et al., 1980a,b; Blau and Gusten, 1981;Behymer and Hites, 1985, 1988; Kamens et al., 1985a,b, 1986; Yokley et al., 1986; Valerio et al.,1987) have concluded that photolysis rates are highly substrate dependent, with darker substratesleading to lower photolysis rates (presumably due to stabilization of the PAH incorporated in theparticles). Cope and Kalkwarf (1987) investigated the photooxidation of certain adsorbedoxy-PAH and found them to be generally stable in sunlight, but to decay under the influence oflight and O . 3
Gas-phase PAH appear to dominate over particle-phase PAH in the formation of nitro-PAHand other PAH-derivatives in the atmosphere (Arey et al., 1987, 1989a, 1990a; Atkinson et al.,1988; Zielinska et al., 1989b, Atkinson and Arey, 1994). Most of the atmospheric transformationproducts of the gas-phase PAH remain unidentified.
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1. Loss Processes for the Gas-phase PAH and PAH-derivatives Gas-phase PAH and PAH-derivatives undergo wet and dry deposition, photolysis, and
reaction with OH radicals, NO radicals, and O . 3 3
a. Wet and Dry DepositionGas-phase PAH have washout ratios ranging from 10 to 10 , while particle-associated PAH2 4
generally have washout ratios around 10 (Ligocki et al., 1985a; Bidleman, 1988). Comparison5+1
of the washout ratios for gas-phase PAH with the time-scale of gas-phase chemical reactionssuggest that rain will not effectively remove them from the atmosphere. Dry deposition is alsoexpected to be of minor importance (Eisenreich et al., 1981).
b. Reaction with the OH RadicalOH radical reactions with the PAH and PAH-derivatives proceed by OH radical addition to
the aromatic ring (forming an initially energy-rich hydroxycyclohexadienyl-type radical), or by OHradical interaction with the substituent groups (either through H atom abstraction from C-H orO-H bonds or OH radical addition to >C=C< bonds: Atkinson, 1986; Atkinson, 1989).
The observed products of OH radical-initiated reactions (in the presence of NO ) with PAHx
and PAH-derivatives are hydroxy- and nitro-arenes (Atkinson et al., 1987). The available (andlimited) data indicate that yields of the hydroxyarenes are significantly higher than those of thenitroarenes.
c. NO Radical Reactions3
Reactions involving the initial addition of a NO radical to the aromatic ring of a PAH lead to3
the formation of nitroarenes (Pitts et al., 1985a; Sweetman et al., 1986; Atkinson et al., 1987,1990; Zielinska et al., 1989a; Arey et al., 1989b). Reactions involving NO radical interaction3
with the substituent group(s) do not lead to the formation of nitroarenes (Atkinson, 1990). Theother products of this type of reaction are not known with any certainty, although they mayinclude hydroxynitro-PAH.
d. O Reactions3
For the gas-phase PAH studied to date, only acenaphthylene has been observed to react withO (Atkinson and Aschmann, 1988), but reaction is also expected to occur for acephenanthrylene3
(Zielinska et al., 1988). These PAHs react with O by addition of O at the cylcopenta-fused ring3 3
>C=C< bond (Atkinson and Aschmann, 1988).
e. PhotolysisNo evidence has been observed for the gas-phase photolysis of the 2- to 4-ring PAH
(Atkinson et al., 1984; Biermann et al., 1985; Atkinson and Aschmann, 1986, 1988). However,photolysis of 1- and 2-nitronaphthalene and 2-methyl-1-nitronaphthalene has been observed underambient outdoor sunlight conditions (Atkinson et al., 1989; Arey et al., 1990b).
C. Atmospheric Lifetimes of Gas-phase PAH and PAH-derivatives
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Photolysis and reaction rate data have been combined with the ambient radiation flux andambient concentrations of OH and NO radicals, NO and O to estimate the lifetimes for some of3 2 3
the PAH and PAH-derivatives. These lifetime data are given in Table VI-1.
The ambient concentrations of NO radicals in the lower troposphere over continental areas3
vary widely, in contrast to O and OH radical concentrations which stay at reasonably consistent3
day-to-day ambient levels (Logan, 1985; Prinn et al., 1987; Arey et al., 1989a).
For the PAH that don't contain cyclopenta-fused rings, the dominant tropospheric lossprocess is by reaction with the OH radical, with calculated lifetimes of 1 day or less (the OHradical reaction only occurs during daylight hours).
The PAH containing cyclopenta-fused rings (such as acenaphthene, acenaphthylene, andacephenanthrylene) are expected to react with NO radicals at a significant rate. NO radical3 3
addition to the fused rings of the PAH is not significant as a tropospheric loss process for thePAH. PAH like acenaphthylene, having unsaturated cyclopenta-fused rings, are also expected toreact with O at a significant rate.3
The dominant tropospheric removal process for the gas-phase PAH appears to be by daytimereaction with the OH radical, leading to lifetimes of about 1 day or less.
Many of the nitroarenes observed in ambient air are only formed in the atmosphere throughthe gas-phase reactions of the 2- 3- and 4-ring PAH (Pitts et al., 1985b; Nielsen and Ramdahl,1986; Sweetman et al., 1986; Arey et al., 1986, 1987, 1989a,b, 1990a; Ramdahl et al, 1986;Zielinska et al., 1988, 1989a,b; and Atkinson et al., 1988).
The presence of the nitro-substituent group in the nitroarenes leads to a marked decrease intheir reactivity towards the OH radical. Photolysis may be the dominant tropospheric removalprocess for these compounds, with calculated lifetimes of about 2 hours.
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Table VI-1The Atmospheric Lifetimes of Selected PAH and PAH-derivatives due to Photolysis
and Gas-phase Reaction with OH and NO Radicals, and O3 3
Lifetime due to reaction with PAHs OH NO O a b c
3 3
Photolysis d
___________________________________________________________________________ Naphthalene 8.6 hrs 100 days >80 days 1-Methylnaphthalene 3.5 hrs 50 days >125 days 2-Methylnaphthalene 3.6 hrs 40 days >40 days 2,3-Dimethylnaphthalene 2.4 hrs 25 days >40 days Biphenyl 2.1 days >20 yrs >80 days Acenaphthene 1.8 hrs 2.5 hrs >30 days Acenaphthylene 1.7 hrs 13 mins ~43 mins Phenanthrene 6.0 hrs Anthracene 1.4 hrs Fluoranthene ~3.7 hrs ~85 dayse
Pyrene ~3.7 hrs ~30 dayse
1-Nitronaphthalene 2.9 days 3.6 yrs >28 days 1.7 hrs 2-Nitronaphthalene 2.8 days 4.0 yrs >28 days 2.2 hrs 1,4-naphthoquinone 5.0 days 100 days >80 days ~2.6 hrs 2-Methyl-1-nitro- 1.8 days 4.0 yrs >55 days 2.1 hrs naphthalene-------------------------------------------------
For a 12-hr daytime average OH radical concentration of 1.5 x 10 molecule cm (Prinn et a 6 -3
al., 1987).
For a 12-hr average nighttime NO radical concentration of 2.4 x 10 molecule cm and an b 8 -33
NO concentration of 2.4 x 10 molecule cm (Atkinson et al., 1986).212 -3
For a 24-hr average O concentration of 7 x 10 molecule cm (Logan, 1985). c 11 -33
For an average 12-hr daytime NO photolysis rate of J = 5.2. x 10 s .d -3 -12 NO2
Using estimated OH radical reaction rate constant correlation with ionization potential e
(Biermann et al., 1985; Arey et al., 1990b; Atkinson et al., 1990).______________________________________________________________________________
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D. Atmospheric Reactions of Gaseous Species
Gaseous diesel exhaust species (such as benzene or formaldehyde) can react in theatmosphere with other pollutants and/or sunlight to form new species. For example,1,3-butadiene can react in the atmosphere with OH radicals and O to form formaldehyde,3
acrolein, and/or radicals (ARB, 1992). Gaseous diesel exhaust species will primarily react with thefollowing:
< sunlight (through photolysis), < O ,3
< the OH radical (during the daylight hours), < the NO radical (during the nighttime hours),3
< gaseous HNO ,3
< NO , and2
< the HO radical (mainly during afternoon/evening hours). 2
The important reaction processes for most of the gas-phase organics are photolysis andreaction with O and the OH and NO radicals. For a limited number of compounds, one or more3 3
of the other reactive chemical species (HO , NO , and/or HNO ) may react with them at2 2 3
significant rates. For example, HO radicals react with formaldehyde, acetaldehyde, and glyoxal;2
NO reacts with conjugated dienes; and gaseous HNO reacts with the amines. 2 3
Gaseous species absorbed by particles may be unavailable for further chemical reaction. Gaseous species adsorbed to particles may be degraded by photolysis and reaction withtropospheric O , N O , NO , HNO , nitrous acid (HONO), sulfuric acid (H SO ), and hydrogen3 2 5 2 3 2 4
peroxide (H O ). 2 2
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E. References for Chapter VI
ARB (Air Resources Board), 1992. Proposed Identification of 1,3-Butadiene as a Toxic Air Contaminant. Technical Support Document, Part A, May. Stationary Source Division.
Arey J., Zielinska B., Atkinson R., Winer A.M., Ramdahl T. and J.N. Pitts, Jr., 1986. The formation of nitro-PAHs from the gas-phase reactions of fluoranthene and pyrene with the OH radical in the presence of NO . Atmos. Environ., 20, 2339-2345.x
Arey J., Zielinska B., Atkinson R. and A.M. Winer, 1987. Polycyclic aromatic hydrocarbon and nitroarene concentrations in ambient air during a winter-time high-NO episode in the x
Los Angeles basin. Atmos. Environ., 21, 1437-1444.
Arey J., Atkinson R., Zielinska B. and P.A. McElroy, 1989a. Diurnal concentrations of volatile polycyclic aromatic hydrocarbons and nitroarenes during a photochemical air pollution episode in Glendora, California. Environ. Sci. Technol., 23, 321-327.
Arey J., Zielinska B., Atkinson R. and S.M. Aschmann, 1989b. Nitro-arene products from the gas-phase reactions of volatile polycyclic aromatic hydrocarbons with the OH radical and N O . Int. J. Chem. Kinet., 21, 775-799.2 5
Arey J., Zielinska B., Atkinson R. and P.A. McElroy, 1990a. Experimental Investigation of the Atmospheric Chemistry of Aromatic Hydrocarbons and Long-Chain Alkanes. UC Riverside.Under ARB Contract No. A032-067.
Arey J., Atkinson R., Aschmann S.M. and D. Schuetzle, 1990b. Experimental Investigation of the Atmospheric Chemistry of 2-Methyl-1-nitronaphthalene and a Comparison ofPredicted Nitroarene Concentrations with Ambient Air Data. Polycyclic Aromat.Compounds, 1, 33-50.
Atkinson R., 1986. Kinetics and Mechanisms of the Gas-phase Reactions of the Hydroxyl Radical with Organic Compounds under Atmospheric Conditions. Chem. Rev., 86, 69-201.
Atkinson R., 1989. Kinetics and Mechanisms of the Gas-phase Reactions of the Hydroxyl Radical with Organic Compounds. J. Phys. Chem. Ref. Data, Monograph. 1, 1-246.
Atkinson R., 1990. Gas-phase Tropospheric Chemistry of Organic Compounds: a Review. Atmos.Environ., 24A, 1-41.
References for Chapter VI (continued)
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Atkinson R. and J. Arey, 1994. Atmospheric chemistry of gas-phase PAH: formation of atmospheric mutagens. Environ. Health Persp.
Atkinson R. and S.M. Aschmann, 1986. Kinetics of the reactions of naphthalene, 2-methylnaphthalene,and2,3-dimethylnaphthalenewithOHradicals withO at3
295 +1K. Int. J.Chem.Kinet.,18,569-573.
Atkinson R. and S.M. Aschmann, 1988. Kinetics of the reactions of acenapthene and acenaphthylene and structurally-related aromatic compounds with OH and NO radicals, 2
N O and O at 296 + 2K. Int. J. Chem. Kinet., 20, 513-539.2 5 3
Atkinson R., Aschmann S.M. and J.N. Pitts, Jr., 1984. Kinetics of the reactions of naphthalene and biphenyl with OH radicals and with O at 294 + 1 K. Environ. Sci. 3
Technol., 18, 110-113.
Atkinson R., Winer A.M. and J.N. Pitts, Jr., 1986. Estimation of night-time N O 2 5
concentrations from ambient NO and NO radical concentrations and the role of N O in 2 3 2 5
Atkinson R., Arey J., Zielinska B. and S.M. Aschmann, 1987. Kinetics and products of the gas-phase reactions of OH radicals and N O with naphthalene and biphenyl. Environ. Sci. 2 5
Technol., 21, 1014-1022.
Atkinson R., Arey J., Winer A.M., Zielinska B., Dinoff T.M., Harger W.P. and P.A. McElroy, 1988. A Survey of Ambient Concentrations of Selected Polycyclic Aromatic
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Hydrocarbons (PAH) at Various Locations in California. Final Report, California Air Resources Board Contract No. A5-185-32, May.
Atkinson R., Aschmann S.M., Arey J., Zielinska B. and D. Schuetzle, 1989. Gas-phase Atmospheric Chemistry of 1- and 2-nitronaphthalene and 1,4-naphthoquinone. Atmos. Environ., 23, 2679-2690.
Atkinson R., Arey J., Zielinska B. and S.M. Aschmann, 1990. Kinetics and Nitro-Products of the Gas-Phase OH and NO Radical-Initiated Reactions of Naphthalene-d , Fluoranthene-d ,3 8 10
and Pyrene. Int. J. Chem. Kinet., Vol. 22, 999-1014.
Behymer T.D. and R.A. Hites, 1985. Photolysis of polycyclic aromatic hydrocarbons adsorbed on simulated atmospheric particulates. Environ. Sci. Technol., 19, 1004-1006.
References for Chapter VI (continued)
Behymer T.D. and R.A. Hites, 1988. Photolysis of polycyclic aromatic hydrocarbons adsorbed on fly ash. Environ. Sci. Technol., 22, 1311-1319.
Biermann H.W., Mac Leod H., Atkinson R., Winer A.M. and J.N. Pitts, Jr., 1985. Kinetics of the gas-phase reactions of the hydroxyl radical with naphthalene, phenanthrene, and anthracene. Environ. Sci. Technol., 19, 244-248.
Blau, L. and H. Gusten, 1981. Quantum yields of the photodecomposition of polynuclear aromatic hydrocarbons adsorbed on silica gel. In: Aromatic Hydrocarbons, M. Cooke, A. J.Dennis and G. L. Fisher (Eds.), Battelle Press, Columbus, OH, pp. 133-144.
Cope, V. W. and D. R. Kalkwarf, 1987. Photooxidation of selected polycyclic aromatic hydrocarbons and pyrenequinones coated on glass surfaces. Environ. Sci. Technol., 21, 643-648.
Coutant, R. W., Brown, L., Chuang, J. C., Riggin, R. M. and R. G. Lewis, 1988. Phase distribution and artifact formation in ambient air sampling for polynuclear aromatic hydrocarbons. Atmos. Environ., 22, 403-409.
Eisenreich, S. J., Looney, B. B. and J. D. Thornton, 1981. Airborne organic contamination in the Great Lakes ecosystem. Environ. Sci. Technol., 15, 30-38.
Finlayson-Pitts, B. J. and J. N. Pitts Jr., 1986. Atmospheric Chemistry: Fundamentals and Experimental Techniques. John Wiley and Sons, Publisher. New York, New York.
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Graedel, T. E., and C. J. Weschler, 1981. Chemistry within aqueous atmospheric aerosols and raindrops. J. Geophys. Res., 19, 505-539.
Kamens, R. M., Perry, J. M., Saucy, D. A., Bell, D. A., Newton, D. L., and B. Brand, 1985a. Factors which influence polycyclic aromatic hydrocarbon decomposition on wood smoke particles. Environ. Int., 11, 131-136.
Kamens, R., Bell, D., Dietrich, A., Perry, J. Goodman, R., Claxton, L., and S. Tejada, 1985b. Mutagenic transformations of dilute wood smoke systems in the presence of ozone and nitrogen dioxide. Analysis of selected high-pressure liquid chromatography fractions from wood smoke particle extracts. Environ. Sci. Technol., 19, 63-69.
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References for Chapter VI (continued)
Kamens, R. M., Fulcher, J. N. and G. Zhishi, 1986. Effects of temperature on wood soot PAHs decay in atmospheres with sunlight and low NOx. Atmos. Environ., 20, 1579-1587.
Korfmacher, W. A., Natusch, D. F. S., Taylor, D. R., Mamantov, G. and E. L. Wehry, 1980a. Oxidative transformations of polycyclic aromatic hydrocarbons adsorbed on coal fly ash. Science, 207, 763-765.
Korfmacher, W. A., Wehry, E. L., Mamantov, G. and D. F. S. Natusch, 1980b. Resistance to photochemical decomposition of polycyclic aromatic hydrocarbons vapor-adsorbed on coal fly ash. Environ. Sci. Technol., 14, 1094-1099.
Leuenberger, C., Ligocki, M. P., and J. F. Pankow, 1985. Trace organic compounds in rain. 4. Identities, concentrations and scavenging mechanisms for phenols in urban air and rain. Environ. Sci. Technol., 19, 1053-1058.
Ligocki M. P., Leuenberger C. and J.F. Pankow, 1985a. Trace organic compounds in rain - III. Particle scavenging of neutral organic compounds. Atmos. Environ., 19, 1619-1626.
Ligocki M.P., Leuenberger C. and J.F. Pankow, 1985b. Trace organic compounds in rain - II. Gas scavenging of neutral organic compounds. Atmos. Environ., 19, 1609-1617.
Logan J.A., 1985. Tropospheric ozone: seasonal behavior, trends, and anthropogenic influence. J. Geophys. Res., 90, 10463-10482.
Nielsen T. and T. Ramdahl, 1986. Discussion on "Determination of 2-nitrofluoranthene and 2-nitropyrene in ambient particulate matter: evidence for atmospheric reactions". Atmos. Environ., 20, 1507.
Pierson W.R., Gorse R.A., Jr., Szkariate A.C., Brachaczek W.W., Japar S.M., Lee F.S.C., Zweidinger R.B. and L.D. Claxton, 1983. Mutagenicity and chemical characteristics ofcarbonaceous particulate matter from vehicles on the road. Environ. Sci. Technol., 17, 31-44.
Pitts J.N., Jr., Van Cauwenberghe K.A., Grosjean D., Schmid J.P., Fitz D.R., Belser W.L., Jr., Knudson G.B. and P.M. Hynds, 1978. Atmospheric reactions of polycyclic aromatichydrocarbons: facile formation of mutagenic nitro derivatives. Science, 202, 515-519.
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References for Chapter VI (continued)
Pitts J.N., Jr., Lokensgard D.M., Ripley P.S., Van Cauwenberghe K.A., Van Vaeck L., Shaffer S.D., Thill A.J. and W.L. Belser, Jr., 1980. "Atmospheric" epoxidation of benzo[a]pyrene by ozone: formation of the metabolite benzo[a]pyrene-4,5-oxide. Science, 210, 1347-1349.
Pitts J.N., Jr., Atkinson R., Sweetman J.A. and B. Zielinska, 1985a. The gas-phase reaction of naphthalene with N O to form nitronaphthalenes. Atmos. Environ., 19, 701-705.
Pitts J.N., Jr., Sweetman J.A., Zielinska B., Winer A.M. and R. Atkinson, 1985b. Determination of 2-nitrofluoranthene and 2-nitropyrene in ambient particulate matter: Evidence for atmospheric reaction. Atmos. Environ., 19, 1601-1608.
Prinn R., Cummold D., Rassmussen R., Simmonds P., Alyea F., Crawford A., Fraser P. and R. Rosen, 1987. Atmospheric trends in methylchloroform and the global average for the hydroxyl radical. Science, 238, 945-950.
Ramdahl T., Zielinska B., Arey J., Atkinson R., Winer A.M. and J.N. Pitts, Jr., 1986. Ubiquitous occurrence of 2-nitrofluoranthene and 2-nitropyrene in air. Nature, 321,
425-427.
Sweetman J.A., Zielinska B., Atkinson R., Ramdahl T., Winer A.M. and J.N. Pitts, Jr., 1986. A possible formation pathway for the 2-nitrofluoranthene observed in ambient particulateorganic matter. Atmos. Environ., 20, 235-238.
Valerio F., Antolini E. and A. Lazzarotto, 1987. A model to evaluate half- lives of PAHs naturally occurring on airborne particulate. Intern. J. Environ. Anal. Chem., 28, 185-196.
Van Cauwenberghe K., Van Vaeck L., and J.N. Pitts, Jr., 1979. Physical and Chemical Transformations of Organic Pollutants During Aerosol Sampling. Adv. Mass Spectrom., 8,
1499.
Yokley R.A., Garrison A.A., Wehry E.L. and G. Mamantov, 1986. Photochemical transformation of pyrene and benzo[a]pyrene vapor-deposited on eight coal stack ashes. Environ. Sci. Technol., 20, 86-90.
Zielinska B., Arey J., Atkinson R. and P.A. McElroy, 1988. Nitration of acephenanthrylene under simulated atmospheric conditions and in solution and the presence of nitroacephenanthrylene(s) in ambient air. Environ. Sci. Technol., 22, 1044-1048.
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References for Chapter VI (continued)
Zielinska B., Arey J., Atkinson R. and P.A. McElroy, 1989a. Formation of methylnitronaphthalenes from the gas-phase reactions of 1- and 2-methylnaphthalene with OH radicals and N O and their occurrence in ambient air. Environ. Sci. Technol., 23, 2 5
723-729.
Zielinska B., Arey J., Atkinson R., and A.M. Winer, 1989b. The nitroarenes of molecular weight 247 in ambient particulate samples collected in Southern California. Atmos. Environ., 23, 223-229.
APPENDIX A
SPECIES/SPECIES GROUPS IDENTIFIED OR TENTATIVELY IDENTIFIED INDIESEL EXHAUST
Appendix A-1
Appendix A
Species/Species Groups Identified orTentatively Identified in Diesel Exhaust
The substances below have either been detected in diesel exhaust or presumed to be in dieselexhaust based on observed chemical reactions and/or their presence in the fuel or lubricating oil. Further research is needed to estimate their contribution to diesel exhaust as a whole, and todiesel exhaust related atmospheric exposures.
Species/Species Groups Identified or Tentatively Identified in Diesel Exhaust
1. ARB, 1993. Emissions profile information received under the AB 2588 Toxics Hot Spots reporting program, including information from the Ventura County Air Pollution Control
Appendix A-11
District (1991), the Naval Energy and Environmental Support Activity (1982), and theHalliburton Equipment Yard (1992).
2. Choudhury, D. R., 1982. Characterization of Polycyclic Ketones and Quinones in Diesel Emission Particulates by Gas Chromatography/Mass Spectrometry. Environmental Scienceand Technology, 16, pp. 102-106.
3. Diesel Exhaust Conference, March 19-20, 1990. Risk Assessment of Diesel Exhaust: 1990 and Beyond. Sponsored by Air Resources Board. Los Angeles, CA.
4. International Agency for Research on Cancer, 1989. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Diesel and Gasoline Engine Exhausts and Some Nitroarenes, Monograph 46, pp. 41-57.
5. Jensen, T. E., 1983. Aromatic Diesel Emissions as a Function of Engine Conditions. Analytical Chemistry, 55, pp. 594-599.
6. Newton, D. L., Erickson, M. D., Tomer, K. B., Pellizzari, E. D., and P. Gentry, 1982.
Identification of Nitroaromatics in Diesel Exhaust Particulate Using GasChromatography/Negative Ion Chemical Ionization Mass Spectrometry and OtherTechniques. Environmental Science and Technology, 16, pp. 206-213.
7. Omni Environmental Services Inc., 1989. Identification of Particulate Matter Species Profile. ARB Speciation Manual, June 30, V. 2, Table 3: PM Species Profile.
8. Pitts, J. N., Jr., Lokensgard, D. M., Harger, W., Fisher T. S., Mejia, V., Schuler, J. J., Scorziell, G. M., and Y. A. Kartzenstein, 1982. Mutagens in Diesel Exhaust Particulate. Identification and Direct Activities of 6-Nitrobenzo[a]pyrene, 9-Nitroanthracene,1-Nitropyrene and 5H-Phenanthro[4,5-bcd]pyran-5-one. Muta. Research, 103, pp. 241- 249.
9. Rappaport, S. M., Wang, Y. Y., Wei, E. T., Sawyer, R., Watkins, B. E., and H. Rapoport, 1980. Isolation and Identification of a Direct-Acting Mutagen in Diesel-ExhaustParticulates. Environmental Science and Technology, 14, pp. 1505-1509.
10. Schuetzle, D., 1983. Sampling of Vehicle Emission for Chemical Analysis and Biological Testing. Environmental Health Perspective, 47, pp. 65-80.
11. Volkswagen, 1989. Unregulated Motor Vehicle Exhaust Gas Components. Volkswagen AG, Research and Development (Physico-Chemical Metrology). Project Coordinator: Dr.K. H. Lies. 3180 Wolfsburg 1, F. R. Germany.
Appendix A-12
12. Yergey, J. A., Risbey, T. H., and S. S. Lestz, 1982. Chemical Characterization of Organic Adsorbates on Diesel Particulate Matter. Analytical Chemistry, 54, pp. 354-357.
13. Yu, M., and R.A. Hites, 1981. Identification of Organic Compounds on Diesel Engine Soot. Analytical Chemistry, 53, pp. 951-954.
